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119 bugs in 6

40 bugs in 9

176 bugs in 7

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51 bugs in 8

33 bugs in 10

13 bugs in 4

Other browser bug collection and identification sites:

Specific Opera 8 and Opera 9 bug collection sites

• Opera 9 bugs collection (database) by Remco Lanting. This website has a long list of hundreds of bugs occuring in Opera 9 along with details, interesting notes for each bug.
• Opera 9 CSS bugs by George Chavchanidze
• Opera 8 CSS bugs by George Chavchanidze
• 16 bugs in Opera 9 by Robert Blaut
• Opera 8 CSS bugs by Andrew Gregory
• Bugs in Opera by Nisse Engström
• Bugs reported regarding Opera 8 at Peter-Paul Koch site
• Bugi występujące w przeglądarkach by Zajec (Rafał Miłecki)
• Opera 9 and Opera 10 bugs by Russian Restaurant Magazine
• Replaced inline element increases line-height of following line-boxes if 'vertical-align' is either 'bottom' or 'top' by Lutz-Peter Hooge
• Bugs in Opera 8 at Opera Browser Wiki
• Opera CSS 2.1 test failures by Robert Blaut
• Object Element Test Case - Override Intrinsic size of the object by percentage by W3C QA
• Opera margin disappearance bug by Alan Gresley
• IE/Opera Floats with block elements not aligning by Alan Gresley

Specific Mozilla and Firefox bug collection sites

• CSS 1 bugs in Gecko
• Mozilla bugs at Peter-Paul Koch site
• Firefox CSS 2.1 test failures by Robert Blaut
• Voluntary Product Accessibility Template for Firefox 2 by Mozilla organization, October 2006
• Voluntary Product Accessibility Template for Firefox 3 by Mozilla organization, October 2008
• Mozilla's UAAG Evaluation Report by Mozilla organization, February 2002
• Mozilla's Bugzilla bug reports: this is the publicly accessible bug reports on all Mozilla products. Hundreds of thousands of bug reports are available via Bugzilla. All confirmed and assigned bug reports on Firefox, Seamonkey, Camino, Thunderbird, Sunbird, Minimo, etc. are available to the public.

Specific MSIE 6 bug collection sites

• Collections of CSS 1 bugs, CSS 2.1 bugs and CSS support for MSIE 6 at channel9
• MSIE 6 Crash bugs, MSIE 6 programming bugs, MSIE 6 DOM bugs at channel 9
• Explorer exposed by Holly Bergevin and John Gallant (position is everything)
• MSIE 6 web standards violations by Holly Bergevin and John Gallant (position is everything)
• MSIE 6 Standards Support and related bugs at channel 9
• 122 bugs reported regarding MSIE 6 at Peter-Paul Koch site
• Hixie's evil CSS testcases by Ian Hickson
• CSS bugs in IE 6 by Dan.
• Wrong z-index implementation bugs by Aleksandar Vacić
• Internet Explorer 6 bugs collection by Marc Pacheco
• Internet Explorer 6 bugs collection A very impressive list of testcases by Bruno Fassino. Lots of layout bugs can be found in MSIE 6 in those tests.
• Test of Gallery Floats' bug in IE by A.W.Marczewski
• Pseudo-class, pseudo-element, dynamic pseudo-CSS bugs in MSIE 6 by Ingo Chao
• Lista bugów przeglądarek (głównie Explorera)
• User Agent Accessibility Guidelines (UAAG) 1.0 Evaluation of Internet Explorer 6 (27 March 2002) by Jon Gunderon and Tim Lacy
• Charles Cooke Browser Bugs by Charles Cooke
• John Russell's browser bugs by John Russell

Specific MSIE 7 bug collection sites

• MSIE 7 bug collection (88 bugs) by Peter-Paul Koch
• Internet Explorer 7 bugs collection A very impressive site of testcases done by Bruno Fassino. Floats, abs. and rel. positioning, inline box, line-height, containment, margin, shrink-wrapping, layout, etc. are methodically and systematically tested and measured.
• 49 IE7 beta 2 bugs by Simon Pieters. About 45 of them are still occuring in IE 7 final release!
• 39 MSIE 7 bugs by Dan.
• "No, Internet Explorer did not handle it properly" IE 7 bug collection by Mark Wilton-Jones. An excellent collection of articles and bugs demonstration.
• CSS bugs in MSIE 7 at incutio.com
• Web Bug Track: 45 bugs in Internet Explorer
• MSIE 7 Beta 2 CSS Bugs at projectseven.com
• Internet Explorer 7 bugs collection by Tino Zijdel
• MSIE 7 mass test case by David Hammond (webdevout.net)
• Design detector's IE7 Bugs List by Christopher Hester
• Nick Rigby IE 7 bugs collection by Nick Rigby
• Enhance IE Internet Explorer 7 bug list
• Ingo Turski's IE 7 bugs collection by Ingo Turski
• CSS Articles and tests from Alan Gresley. A very fascinating collection of articles demonstrating convincingly resistant bugs in MSIE 7, including guillotine bug, peekaboo bug, IE Margin Transference Bug, etc. There is also a specific IE 7 bug collection.
• Pseudo-class, pseudo-element, dynamic pseudo-CSS bugs in MSIE 7 by Ingo Chao
• Internet Explorer 7 User Interface bugs by Ben Thomas Millard
• Internet Explorer 7 User Interface report by Daniel Glazman
• Lista bugów przeglądarek (głównie Explorera)
• Charles Cooke Browser Bugs by Charles Cooke
• John Russell's browser bugs by John Russell
• HTML Bugs, Home of the WOPR
• hasLayout.net's CSS bugs in Internet Explorer by Zoffix Znet

Individual testcases or webpages that fail in MSIE 7

• width: auto with block width: 100% by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2, Hv3 TKHTML alpha 16 all pass this test.
• Positioning blocks inside inline contexts with top: auto by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2 all pass this test.
• Table layout: absolute positioning should shrink wrap by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, Amaya 9.54, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2, Hv3 TKHTML alpha 16 all pass this test.
• Negative heights by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2, Hv3 TKHTML alpha 16 all pass this test.
• CSS block box models: first-line and anonymous boxes by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2 all pass this test.
• CSS floats: Unexpected Presences, part 3 by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2 all pass this test.
• Floats inside blocks by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2, Hv3 TKHTML alpha 16 all pass this test.
• Bottom margins on floats by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, Amaya 9.54, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2, Hv3 TKHTML alpha 16 all pass this test.
• Blocks within inline by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2, Hv3 TKHTML alpha 16 all pass this test.
• CSS Inline Box Model: Behaviour near cells by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2, Hv3 TKHTML alpha 16 all pass this test.
• CSS Inline Box Model: Baseline alignment of images by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2, Hv3 TKHTML alpha 16 all pass this test.
• CSS Inline Box Model: Baseline alignment of images by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2, Hv3 TKHTML alpha 16 all pass this test.
• Inline box model: space taken by images in cells by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2, Hv3 TKHTML alpha 16 all pass this test.
• CSS Lists: list-item with list-style-image by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2 all pass this test.
• Tall table with wide L-shaped floats by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 6.2, NS 7.0, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2 all pass this test.
• Scrolling Backgrounds by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2 all pass this test.
• Scrolling Backgrounds by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2 all pass this test. The problem can also be seen at Evil test: Positioning Backgrounds: 3. More Position and 4. Background and Border from Ian "Hixie" Hickson.
• Scrolling Backgrounds in scrolling backgrounds by Ian "Hixie" Hickson. Firefox 2.0.0.4, Safari 2, Safari 3.0.2, Opera 9.21, NS 7.2, K-meleon 1.x, Galeon 2, Epiphany 2 all pass this test.
• The Float model problem by Holly Bergevin and John Gallant (positioningiseverything.net)
• Wrong z-index implementation bugs by Aleksandar Vacić
• List item and hasLayout bugs by Claire (Suzy) Campbell
• Cleared float within relative positioned element by Tino Zijdel. Even NS 6.1 and NS 6.2 render this testcase perfectly.
• IE z-index bug by Tino Zijdel.
• IE7 float bug by Tino Zijdel.
• Convincing IE7 float bug demo by Tino Zijdel.
• Float columns by Patrick Fitzgerald (click this link and then choose the tab "8"). This is the same bug as described in the bug Floats in specified height containers are ignored by following boxes by Bruno Fassino and also at Floats, Margins and Percentage widths
• MSIE 6 and MSIE 7 bug with overflow and position: relative by Emmett the Sane
• Content-type: text/plain: If you send a header that says that you are using plain text, but it contains something that IE thinks is HTML, it will ignore your header, and render it as HTML. by Mark Wilton-Jones.
  W3C Note (Feb. 2001) Common User Agent problems, 3.2 Respect the media type of a resource if one is explicitly given using the Content-Type HTTP header states "If an HTML document is returned with a Content-Type value of text/plain, the user agent must render the document as plain text without interpreting HTML elements and attributes (i.e. the HTML source must be displayed)." while Handling MIME Types in Internet Explorer and MIME Type Detection in Internet Explorer article states "A MIME type is ambiguous if it is 'text/plain', 'application/octet-stream', an empty string, or null (that is, the server failed to provide it). A MIME type that is neither known nor ambiguous is termed unknown. The MIME types 'text/plain' and 'application/octet-stream' are termed ambiguous because they generally do not provide clear indications of which application or CLSID should be associated as the content handler."
• IE 7 Float model by Mark Wilton-Jones.
• :before and :after by Mark Wilton-Jones.
• Multi-columns layouts by Mark Wilton-Jones.
• Empty Elements by Mark Wilton-Jones.
• Add (option) syntax by Mark Wilton-Jones.
• navigator.plugins by Mark Wilton-Jones.
• Empty space (blank white space handling/detection in the DOM) by Mark Wilton-Jones.
• Event model by Mark Wilton-Jones.
• Event objects by Mark Wilton-Jones.
• Errors in valid scripts by Mark Wilton-Jones.
• Link tags: absence of Site Navigation toolbar in IE; from Mark Wilton-Jones. Internet Explorer 6 and Internet Explorer 7 are 2 of the rare graphical web browsers that do not implement the HTML 4 recognized link types as recommended by W3C QA tip for webmasters: Use <link>s in your document and by many accessibility standards groups.
• Alternate stylesheets by Mark Wilton-Jones.
• Object tags by Mark Wilton-Jones.
• Data: URIs by Mark Wilton-Jones.
• Test of Gallery Floats' bug in IE by A.W.Marczewski. The last 2 tests in that page fail in IE 7.
• IE 7 universal selector bug The universal selector selects HTML comments as well and even applies some styles to it. By Klaus Hartl
• Disappearing border-top by Ben Hollis
• Not honoring z-index by Ben Hollis
• Overflow auto and position: relative by Rowan Wigginton. This one has been reported and testcase-ed by many and is a well documented bug afflicting Internet Explorer 7, namely by Jonathan Snook in his Position:relative and overflow in Internet Explorer.
• Float versus Absolute by Rowan Wigginton
• Margin collapsing bug demonstrated by Micah Sittig
• Margin collapsing bug: The hasLayout MS-property affects the collapsing of margins between a box and its descendants by Ingo Chao
• Other convincing demos on margin collapsing bug for nested elements by Bruno Fassino
• Margin collapsing tests by Ben Cotterell
• Internet Explorer 7 does not correctly support PNG gamma correction by David Hammond
• Internet Explorer implements incorrectly the alt attribute (versus the title attribute):
  • Use of ALT text in IMGs; ALT text as "tooltips"? by Alan Flavell ✝
  • Guidelines on alt texts in img elements; The "tooltip" effect and the title attribute by Jukka Korpela
  • The ALT attribute in HTML by Stephen Poley: "Some screen-based browsers display the ALT text temporarily (as a 'tool-tip') if one hovers over the image with a mouse. This is not the intended use of ALT (...)"
  • Use the alt attribute to describe the function of each visual by W3C Quality Assurance tip for webmasters
  • 13.8 How to specify alternate text by W3C HTML 4.01 specification
  • The alt and title attributes by Roger Johansson
  • Titles and alternative text for images; Alt text is not a tooltip by Arve Bersvendsen
  • 9 Ways to Misunderstand Web Standards "The meaning of alt text is to serve as replacement (hence, 'alternative') when the image the HTML intends to serve cannot be seen. There's a variety of reasons for that to happen; the user is blind, the medium doesn't support images, the user disabled images on purpose so (s)he can browse on low-bandwidth, or the Googlebot comes around to visit."

  This bug has been reported at connect's IE beta feedback as bug 334225.

• The alternative text of the IMG element - part 1 by Ian "Hixie" Hickson
• The alternative text of the IMG element - part 2 by Ian "Hixie" Hickson
• IE7 disappearing content bug by Sophie Dennis
• IE 7 bug: nested list (abs. positioned) is overrun by preceding link's background colour by Aleksandar Vacić
• IE 7 bug: abs. positioned element has an implicit value of left right next to right edge of the previously floated element by Aleksandar Vacić
• <object> Element Test Case - Intrisic size of the object by W3C QA
• <object> Element Test Case - Override Intrinsic size of the object by pixels by W3C QA
• <object> Element Test Case - Override Intrinsic size of the object by percentage by W3C QA
• <object> Element Test Case - Insert an ascii text (HTML source code) without encoding information from the server and the client by W3C QA
• <object> Element Test Case - Include the full object with data attribute and data: scheme by W3C QA
• IE7 absolutely positioned italics by Stuart Colville
• Overlapping elements by Dan. This demo page is rendered as expected by Firefox 1.5.x, Firefox 2, NS 7.2, Safari 2, Konqueror 3.x, MSIE 6, Seamonkey 1.1, Opera 9.20, Amaya 9.54
• Menu shifting unexpectedly by Dan. This demo page is rendered as expected by Firefox 2, Safari 2, NS 7.2, Opera 9.20, Seamonkey 1.1
• hasLayout bug: container shifts and overflows unexpectedly when hovering a link by Dan. This demo page is rendered as expected by Firefox 2, Safari 2, Opera 9.20, NS 7.2, Seamonkey 1.1
• IE 7 star hack problem by Dan. This demo page is rendered as expected by Firefox 2, Safari 2, Opera 9.20, NS 7.2, Seamonkey 1.1.
• Padding occurring unexpectedly by Dan. This demo page is rendered as expected by Firefox 2, Safari 2, Opera 9.20, NS 7.2, Seamonkey 1.1.
• List-style, height, line-height and child selector by Dan. This demo page, is rendered as expected by Firefox 2, Safari 2, Opera 9.20, NS 7.2, Seamonkey 1.1.
• Footer problem by Dan. This demo page is rendered as expected by Firefox 2, Safari 2, Opera 9.20, NS 7.2, Seamonkey 1.1.
• Padding not applied by IE 7 by Dan. This demo page is rendered as expected by Firefox 2, Safari 2, Opera 9.20, NS 7.2, Seamonkey 1.1, Amaya 9.54.
• Images disppear when hovering with IE 6 or IE 7. by Dan. This demo page is rendered as expected by Firefox 2, Safari 2, Opera 9.20, NS 7.2, Seamonkey 1.1, Amaya 9.54.
• Height and IE 7 by Dan. This demo page is rendered as expected by Firefox 2, Safari 2, Opera 9.20, NS 7.2, Seamonkey 1.1.
• Border not displayed when hovering with Internet Explorer without position:relative by Dan. This demo page is rendered as expected by Firefox 2, Safari 2, Opera 9.20, NS 7.2, Seamonkey 1.1.
• setAttribute("class", "a_class_name") bug by Richard Cunningham
• Object getElementsByTagName by John Resig
• Missing border after scroll: position relative and hasLayout by Claire (Suzy) Campbell
• Floats and disappearing absolutely positioned boxes. MSIE 6 and MSIE 7 fail test 1, test 2 and test 12! by Bruno Fassino. These 20 tests are rendered as expected by Firefox 2, Safari 2, Safari 3.0.2, Opera 9.22, NS 7.2, Seamonkey 1.1, K-meleon 1.x, Galeon 2, Epiphany 2.
• Top and bottom values of vertical alignment of images (and other content) inside line boxes with assigned line-height are ignored by Bruno Fassino
• nested list (abs. positioned) is overrun by preceding link's background colour by Aleksandar Vacić
• Internet Explorer 6 and Internet Explorer 7 will CRASH when loading (IE 6) and when resizing (IE 7) a page with <style>*{position:relative}</style><table><input></table>. This crash bug has been confirmed by many people so far. Crashs in IE7 as well if you open the page then maximize it,, Deviance; Indeed, IE7 does not crash until the window is maximized., Jon; Confirmed: Crashes IE7 on a fresh install of Windows Vista Premium and with Windows Vista Premium with all patches applied if you open the link then attempt to resize the window at all., Robert.
• A stylesheet sent as content-type text/plain shouldn't be interpreted by the browser as CSS. It should instead be ignored. by David Hammond
• IE7 applies the min-width value as width on input elements with @type values of button, reset, and submit by Steve Ganz
• IE6 and IE7 not calculating position of a non-floated div correctly by Marc Pacheco
• Vertical-align property do not (and should not) apply to <col> elements by Ian "Hixie" Hickson. This demo page is rendered as expected by Firefox 2.0.0.3, Safari 2.0.4, Opera 9.20, Seamonkey 1.x and Konqueror 3.5.5.
• IE7 using unnecessary horizontal scrollbar caused by italics by Bruno Fassino
• IE7 bug: will not render z-index change on li:hover by Aleksandar Vacić. This reduced testcase clearly shows the issue.
• IE7 float clearing by Aleksandar Vacić. MSIE 7 incorrectly interprets height:1% rule as it automatically expands the height of a box in question if its floated content can't fit.
• Input sizing in IE: non-resizable input font-size by Aleksandar Vacić. This reduced testcase clearly shows the issue.
• IE 7 background painting bug by Christopher Hester
• IE/Win problems with absolute positioning inside a relative element by Bruno Fassino
• Stacking of overlapping boxes (involving negative vertical margin) is wrongly affected by hasLayout by Bruno Fassino. The demo even shows a case where layout changes after an hover effect.
• Externally Declared Global Variable Leak in MSIE 6 and MSIE 7 by Mark Wubben. When creating circular references between window objects and declared global variables (someWindow.globalVariable) on window object A from window object B (or vice versa), these variables will leak even if they are not referenced.
• Italic text overlap floats in IE7 from straatadvocaat.org, by Danny van der Ben
• The return of the Guillotine bug in MSIE 7! by Alan Gresley. A very convincing article with demos and explanations.
• Sticky Sons of Suckerfish or the IE7 re-calculated offset with hover on or off bug by Alan Gresley. A very convincing article with demos and explanations.
• IE margin transference bug by Alan Gresley. Gap appear unexpectedly between a float and a clearing block-level element because IE transfers or duplicates the bottom margin.
• IE 7 Peekaboo Type Bug by Alan Gresley.
• The stretched buttons problem in IE by David Grudl. HTML buttons are unnecessarily too wide and large buttons are rendered jagged and weird. This problem is also reported by several other web developers, including Jehiah Czebotar with his An Even Better IE Button Width Fix.
• MSIE 7 does not support Base64 encoded images by Dean Edwards
• In-page links and keyboard navigation by Jim Thatcher. MSIE 7 can not give, transfer focus to input via keyboard. Also his More on In-page links and the IE Bug article covers the issue.
• Pure CSS hover list (Listamatic 2: nested lists) from CSS MaxDesign.
• Background-color painting failure from Chris Hester. MSIE 6 and MSIE 7 fail to paint the background-color of bottom div fully when the window is narrowed.
• CSS bugs affecting a CSS columnar layout in MSIE 7 by Ingo Turski. At least 4 bugs in MSIE 7 affect this page layout.
• Borders unexpectedly appears in MSIE 7 by Jukka Korpela. The bug is explained in details in the "An odd IE 7 bug with :first-letter, link, and border" posted message at incutio.com
• Listamatic: CSS 3 corporate fun (horizontal nested lists) by Sander van Dragt.
• IE Float model and the reality by Alan Gresley.
• Attribute nightmare in IE An article on getAttribute and attributes collection bugs by Tobie Langel
• MSIE 7 does not support type="application/ecmascript" and type="application/javascript" which meet RFC 4329. The valid types are "application/javascript" and "application/ecmascript". All modern JavaScript interpreters being implementations of ECMAScript, it seems like it would be best to use "application/ecmascript". Except that our good friend IE doesn't recognize them and ignores the script altogether if you use them. So once again, thanks to one more non-standard behavior of IE, we can't afford to follow the standard. by Bertrand Le Roy.
  RFC 4329 was published in April 2006 and RFC 4329 was discussed and approved as soon as June 2005
• Internet Explorer should stop automatically requesting for favicon.ico in the root directory - a file which may not exist - and instead look for (fetch, HTTP request) an icon only and only if it's explicitly linked to from the webpage. The first time a user visits your Web page, Internet Explorer automatically searches for this [favicon.ico] file. Otherwise, when the favicon.ico does not exist, the error.log shows favicon.ico (hundreds of times) as "404 file not found". From a web standards and HTTP perspective, it does not make any sense to request a file that has not been explicitly linked to begin with. This bug has been reported by several web authors since 1997!:
  • Dan's Web Tips: Titles, META Tags, LINK tags, and Search Engine Robots by Dan Tobias states: "MSIE automatically looks for 'favicon.ico' in the root directory of your site (which some webmasters find annoying if they have no desire to use an icon and don't like getting lots of '404 Not Found' errors in their log), some other browsers, like Mozilla, are more considerate and only look for an icon if it's explicitly linked."
  • Top 10 Bugs, Internet Explorer by Toby Inkster states: "Stop automatically requesting /favicon.ico and instead only request it when it's explicitly linked to from the page."
  • Web standards checklist, 6.4 Does the site have a favicon? by Russ Weakley states: "if they [favicon.ico] are not present, they can cause 404 errors in your logs (site statistics). Browsers like IE will request them from the server when a site is bookmarked. If a favicon isn't available, a 404 error may be generated."
• Internet Explorer 6 and Internet Explorer 7 generate a vertical scrollbar when an horizontal scrollbar is generated by an horizontal overflow. Fixing the IE Overflow Vertical Scrollbar Bug by Josh Stodola: "I use IE exclusively and I think it is the fastest loading browser available. But, I would never shy away from admitting that it is loaded with annoying bugs. A common one you will see is how it interprets the overflow:auto style when there is enough text to force a horizontal overflow. When there is enough text to make it overflow horizontally, you will always get a vertical scrollbar (regardless of whether or not a true vertical overflow exists). It's like the containing element does not account for the height of the scrollbar itself!"
• Internet Explorer 6 & Internet Explorer 7 document.domain bug
• Internet Explorer 7 SELECT element innerHTML bug by Alex Le
• cloneNode() and removeChild() are broken by Jehiah Czebotar
• CSS parsing bug on background-image by Andrew Walker
• Another CSS parsing bug involving counters by Andrew Walker
• Internet Explorer 7 and the float bottom margin bug by Marko Dugonjić from his article IE 7 quirks: floats and margins, here we go again
• Floats and margins testcases by Florent Verschelde. This webpage shows 3 tests out of 5 that Internet Explorer 7 fails. The webpage is in French but is rather easy to figure out and to understand.
• <style type="text/css"> @import url(css/styles.css) screen;</style> is not supported by Mathieu "mEga" Recchia. The webpage is in French but rather easy to figure out and to understand.
• CSS Layout Example 1 and CSS Layout Example 2 by Stephen Poley are 2 CSS columnar webpage templates which fail in Internet Explorer 7 but do not fail in Internet Explorer 6.
• Favicon standardisation and Architecture of the World Wide Web, 2.5 URI opacity state that the href of a favicon should point to any URL and not be limited, not be restrained to the location of /favicon.ico (at root of server). "The use of a reserved location on a website conflicts with the Architecture of the World Wide Web, and is known as link squatting or URI squatting." The document W3C Quality Assurance tip, How to Add a Favicon to your Site and siteData-36 state that identifiers on a web site should be entirely under the control of the owner/publisher of the domain name.
• Favicon standardisation and HTML 4.01 specification, rel attribute value (link-types) state that the rel attribute must contain a space-delimited list of link types, so a two-word link type like rel="shortcut icon" will not be understood correctly by conforming web browsers. Therefore, Internet Explorer should just follow and conform with the preferred and recommendable method of adding a Favicon to a website as given and explained at W3C Quality Assurance tip, How to Add a Favicon to your Site.
  This issue was also mentioned and explained by Dan Tobias in his Dan's Web Tips: Titles, META Tags, LINK tags, and Search Engine Robots as follows: "MSIE looks only for 'shortcut icon'. Technically, a link attribute with multiple words is saying that the link is of multiple types, with each word being a different type identifier, but I think the Microsoft programmers were just clueless enough to think that spaces could be used within type names, and that 'shortcut icon' is what they think the type is."
• New peekaboo bug in IE 7 demo by Jonathan N. Little. This bug was presented and explained in a google post in comp.infosystems.www.authoring.stylesheets on January 14th 2008. This New peekaboo bug in IE 7 demo webpage is convincingly demonstrating that Internet Explorer 7 still have big problems with some CSS columnar layout templates. Credit must go to Jonathan N. Little.
• No overflow: hidden applied to body by Gregor "hrax" Magdolen from elepha.info. Overflow: hidden is not implemented for body element.
• Internet Explorer 7 Float Bug by Austin Matzko
• IE button bug: When a form has more than one button of type submit with the same name attribute, Internet Explorer will always pass the value of last one on the form no matter which button is pressed. This bug is reported by CpILL's Too much information
• Unclosed <p> before a form messes up form styling on IE 7 and IE 8 by Jukka Korpela. This bug report is very much similar to the implicit closing on an unclosed <p> element when it encounters a <table>. Firefox 2, Firefox 3, Safari 3.1, Opera 9.50, Konqueror 3.5.2, Seamonkey 2.x, K-meleon 1.x, Galeon 2.0.4, Epiphany 2.22 all pass this test.
• <object> element not using image map reference by Chris Haig. This is FeedbackID=333636 at connect.microsoft.com.
• IE 7 bug: declared width for table cell wrongly affects inner block by Jukka Korpela.
• Floaty JavaScript Browser Bugs by Chris Hester. IE makes secondary list items really narrow. And it loses the bullet points too.
• IE7:hover ghosts bug by Vilém Málek. If you nest several elements inside each other and you tie the display of child elements to the :hover of the parent element, it can happen that after a first, correct display of the nested elements, these elements will stay displayed in IE7 even if the element directly above them does not have :hover!
• Margin form bug by Scott Sauyet. This bug is amazing: as the user hovers the mouse over a list of links, the form input and the whole form move down. This bug was also reported by Alan Gresley in his IE/Win Magic Form Bug
• Bullet problem with nested lists and max-width on LI by Tony Suárez (?)
• IE7 doubles the top padding from cafefrenzy.com: "Nothing is more annoying than finishing a web design, having it dispay just the way you like it in your standards compliant browser only to remember to check it in IE and find it a garbled mess. (...)"
• White space bug revisited by Gary Turner. There are cases in which IE treats the white space "\n" between <li> and the next <li> as a literal linefeed. That creates extra space between list items.
• Space between list items in IE by Gary Turner
• Closing the gap between list items in IE by Roger Johansson. "A long-standing bug in Internet Explorer is the gaps it likes to insert between list items that contain block level elements, if there is any whitespace between the list items in the markup. (...) The release version of IE 7 still suffers from it"

Chris Wilson, Internet Explorer 7 and CSS 2.1 compliance

Browser conformance test suites

• HTML 4.01 conformance tests by Robin Lionheart. MSIE 7, Firefox 2, Opera 9, Safari 2 and Icab 3 are tested, measured and their results can be compared.
• Several hundreds of CSS testcases by Ian "Hixie" Hickson. This has to be the most complete, thorough testsuite for modern browsers.
• Several thousands of tests for CSS, HTML, DOM, JavaScript, etc. by Ian "Hixie" Hickson. This has to be the most complete, thorough testsuites for modern browsers.
• Current CSS 2.1 Test suite at W3C (last updated on August 4th 2007). Firefox 3.0a9pre rv:1.9a9pre nightly build 2007092502 fails 27 tests out of 500 (5.4% failure); Opera 9.50a3 build 9542 fails 50 tests out of 500 (10.0% failure); Internet Explorer 7 fails 129 tests out of 500 (25.8% failure); Safari 3.0.3 build 522.15.5 fails 43 tests out of 500 (8.6% failure).
• DOM 1 Core tests by W3C. MSIE 7 fails 85 tests out of 224 tests, a 37.9% rate failure which is well over/above the percentage rate of Firefox 2 (6.3% failure rate) and Opera 9 (5.1% failure rate).
• CSS 3 Selectors test suite results by Robert Blaut
• User Agent Accessibility Guidelines 1.0 Test Suite for HTML 4.01 (draft) by W3C's WAI
• JScript Deviations from ECMAScript 3rd edition (PDF): This 87 pages PDF document (filesize: 784 KB) lists most (but not all) the bugs in Internet Explorer and the differences in the ECMAScript 3rd edition implementations between the 4 major browser manufacturers. The document is a first draft.

• Web Compatibility Test for Mobile Browsers Although aimed at mobile browsers, this test is suitable for screen, visual browsers.

  Browser version	%tage success	Success score
  Internet Explorer 7	50 %	8 tests passed out of 16 tests
  Internet Explorer 8	50 %	8 tests passed out of 16 tests
  Firefox 3.0.9	75 %	12 tests passed out of 16 tests
  Firefox 3.6a2 build 20090326	87.5 %	14 tests passed out of 16 tests
  Fennec/1.0a2	87.5 %	14 tests passed out of 16 tests
  Konqueror 4.2.4	81.3 %	13 tests passed out of 16 tests
  Safari 4.0 build 530.17	93.8 %	15 tests passed out of 16 tests
  Opera 9.64	100 %	16 tests passed out of 16 tests
  Opera 10.0 beta 1	100 %	16 tests passed out of 16 tests