• Mozilla is written in c++, not c.
• gtkhtml is the rendering library (most) gnome apps use as a help browser. And its' "real" html support is heinous
• perl is a great language, but it's not nearly fast enough to be used for an app as complex as a web browser. and i mean a graphical web browsers, not lynx. i have a 1.4ghz athlon, and the slowest app in both windows and linux is still my web browser (ie6 and mozilla 0.9.5).

there is the gecko library (the rendering engine from mozilla) that is freely available. perhaps a gtk frontend could be written in perl. but the galeon people have already done a pretty good job of this in C; if your goal is to make a faster web browser, perl isn't really the right way to go.

and i'm not sure what you mean by the "coolest ones". everyone in my office drools over the tabbed interface mozilla 0.9.5 has, while ie continues to have scripting issues (and won't recognize urlencoded urls as of ie6), and opera costs money.

i should note that i'm a bit biased; i've been using mozilla for the last 2 years (exclusively for the past 16 months). i've submitted and worked on alot of userland bugs and compiler related issues. and to be perfectly honest, i do more web browsing at work with nc and telnet than i do with any browser....