First sentence: this text should be green. The markup code is invalid according to W3C HTML validator and the CSS code is invalid according to W3C CSS validator.

Second sentence: this text should be green according to CSS 1 but it should be red according to CSS 2.1. The markup code is also invalid according to W3C HTML validator but the CSS code is perfectly valid according to W3C CSS validator.

Third sentence: this text should be green. The markup code is valid according to W3C HTML validator but the CSS code is invalid according to W3C CSS validator.

Fourth sentence: this text should be green according to CSS 1 (class name can not start with a dash in CSS 1) but it should be red according to CSS 2.1 and the markup code is valid according to W3C HTML validator and the CSS code is perfectly valid according to W3C CSS validator.

Fifth sentence: this text should be green according to CSS 1 (class name can not start with a dash in CSS 1) but it should be purple according to latest CSS 2.1 WD (class name can not start with a dash unless immediately followed by [_A-Za-z] character in CSS 2.1) and the markup code is valid according to W3C HTML validator and the CSS code is perfectly valid according to the W3C CSS validator!

Valid HTML 4.01!
Validate the CSS code of this page according to CSS 1 profile
Validate the CSS code of this page according to CSS 2.1 profile