This article could really be titled how IE8 measure against W3C and other Web Standards. So this is really a report on progress on picking up the pieces on W3C and Web standards since  Microsoft’s browser  embargo on all feature improvements to IE from 2001 to 2006. The Five Year Freeze imposed by Microsft went well beyond W3C and Web standards  when no new features were added to the IE browser. This functional freeze was effectively imposed on all browsers because Redmond had 90%++ Browser market share and had not only stopped all development plus stalled a substantial amount of work in many W3C and other standards committees from 2000 through 2006 (see for example the history of progress on W3C CSS standards).

After this 5 year drought and dismantling of what had been a huge IE development team except for security fixes, one can imagine the problems that IE would have in coming back up to speed in browser development. Here is a table of how all the major the browsers perform on key Web standards. Note ratios like 88/154 means that IE8 passed 88  of 154 W3C  tests for browsers:

Standards Support in the Major Browsers
Web Standard IE8 Firefox 3.x Chrome 1. Opera 9.6 Safari 4
CSS Stylings 88/154 138/154 146/154 TBD TBD
CSS Colors Test 21/53 52/53 42/53 31/53 48/53
CSS Namespace None 20/22 16/22 15/22 16/22
E4X None Full None None None
JSON Yes Yes Yes Yes Yes
JPEG2000 No No No No No
SMIL No?? 3.1? 2.0? No 4.0?
SVG (see here for browser tests) None 60.4% 61.9% 94.2% 64.2%
XForms 3rd party Partial TBD 3rd party 3rd party

Note red marks worst performing browser, green the best performing browser – ratio scores are (passed tests/total tests). TBD – Tests to Be Determined – results should be appearing in the next 2-3 weeks.

Browsers used in these tests (except in SVG test results) are the latest available as of March 18th, 2009
IE8 – final release 8.0.60001, Chrome 1.0.154, Firefox 3.07, Opera 9.6, Safari 4 beta 528.01

Clearly IE has suffered dramatically from its own long freeze – it is way at the tail end of almost all of the standards. It is also still performance and feature short versus Firefox and all the other browsers. Even Opera, which has seen a decline in its usual standards leading conformance, continues to perform well in speed tests. Yet in the past Microsoft saw fit to throw lots of people and resources at IE development while the current IE team constantly cites resource constrained delays in improving IE vis a vis Web standards and competitive features. But it is in the area of browser speed and performance where IE8 particularly lags behind all the other major browsers and by significant margins. See tests here and here.

In sum, we strongly advise against using IE for web browsing – there are lots of much better alternatives while sites that insist on using IE exclusively are declining as rapidly as IE’s market share:

Source: StatCounter Global Stats – Browser Market Share

As for developers, there is a more thorough analysis of the fitness of IE as Web Development tool upcoming on our main site. But clearly Web 2.0 and JavaScript+DOM+CSS hacks  are now being used by many developers to fill in the gaps in IE8 and other Microsoft Web apps. Many web developers think of it as the Microsoft Web Tax.
Updated for SMIL availability: April 5, 2009
For a more recent [mid August 2009] review of all the browsers, check out Information Week.
Updated for IW browser comparison: September 1, 2009