You can't make a good browser with all the current demands on it: ActiveX, javascript, HTML/XHTML/DHTML (not to mention the myriad versions, proprietary extensions and that kind of crap), HTTP1.0/HTTP1.1, SSL1/SSL2/SSL3/TLS, gif, png, mng, jpeg, mpeg, quicktime, realtime, avi, windows media, sounds (wav/aiff/au/mp3/ogg/mp2/wma), CSS, DOM... you name it.
To me, the killer ones are ActiveX/Javascript (too much for an efficient browser), all the countless proprietary extensions to both HTML/DHTML and JavaSript, and the unholy amount of multimedia content browsers must support in order to have a chance of succeeding.
It's just too complex. Better were the days when a browser simply parsed HTML, with the few casual images in it.
Oh... don't forget WMF!
(yes, you can read it both ways... I prefer the dirty one
![Twisted Evil :twisted:](./images/smilies/icon_twisted.gif)
)