Vertical-align: sub is incorrectly rendered in Internet Explorer 6 and Internet Explorer 7

Actual (live) result in your browser:

vertical-align: sub

Expected result (screen shot 300px wide, 68px tall):

References:
"sub
    subscript the element"
CSS 1, section 5.4.4, vertical-align property

"sub
    Lower the baseline of the box to the proper position for subscripts of the parent's box"
CSS 2.1, section 10.8.1, vertical-align property

Firefox 1.5.x, Firefox 2.0.0.3, Safari 2.0.4, Safari 3.0.2, Opera 9.20, Konqueror 3.5.5, Seamonkey 1.x, NS 6.1, NS 6.2, NS 7.0, NS 7.1, NS 7.2, K-meleon 1.x, Galeon 2.0.2, Epiphany 2.14 all pass this test.