That CGI method looks very interesting. I think I should maybe do a project on it later.
I think people should start using C for web development because web sites are so horrible as well as these high level programming languages that let people copy and paste code or use other people's library without any knowledge of whats happening. I don't want to get into how bad this high level languages but I can say that PHP beats most of the web languages out there and is used for top web sites on the interwebs.
Let me preface with: I like C. I think we should write more things in C.
I do *not* think we should use C for web apps. C is, in general, a poor match for web programming. Most web programming is string manipulation. Parse the request string, build a database query, insert the results in a template page. Strings everywhere. C's stdlib string handling is a disaster. Subtle bugs abound, where "well, it doesn't crash" isn't enough to verify a piece of code even *works*, much less is not a massive security hole.
More to the point, the web app's performance is rarely relevant to the end user. For something like Facebook or Twitter, the app simply makes a database query. Performance bottlenecks are the database (which *is* written in C, in pretty much all cases) and network latency. Unless you're handling millions of queries a second, you don't really care how slow your app itself is.