The W3C does infact dictate how images should be rendered. It also now dictates how videos should be rendered thanks to HTML5 (the latest version of HTML which is an upgrade from HTML4/xHTML) However, some images (I believe .bmp and certain .png) can have their own color palletes which don't play well with Webkit based browsers (Safari and Chrome I believe) not to mention IE6 can't even render PNG's with opaque backgrounds properly (unless you use directx & css hacks)
When it comes to standards Internet Explorer comes in last. There is a test out there called the Acid test which determines how well your web browser supports standards. 0 means it supports zero standards, 100 meaning it supports all standards.
In order from Worst to Best here is the results for the second iteration of the test,
The Acid3 Test
- Google Chrome: 100/100
- Opera: 100/100
- Safari: 100/100
- Mozilla Firefox: 94/100
- Internet Explorer 8: 20/100
- Internet Explorer 7: 14/100
- Internet Explorer 6: 12/100
Let that be an example of how far behind IE is, HOWEVER. there is some light at the end of the tunnel. Beta versions of Internet Explorer 9 are scoring 92/100. Of course this is a beta version and Microsoft can always remove and add features.
Second, we will have to look at HTML5 and CSS3 support. This is the future of the web and some websites are already deploying these technologies. IE6, 7 and 8 support almost NOTHING of the kind. Whereas all the other browsers (Safari, Opera, Firefox and Chrome) support around 80~95% of all the new features in CSS3 and HTML5.