There are many different HTTP servers, the most used are:
Apache - Freeware http server.
Used on about 60% of the Web sites. Runs on anything, stable, secure
and fast. This is the best one.
MS IIS. Free. Runs on NT only. Runs on about 20% of the Web sites.
Much less secure than apache, if you don't belive it check the
vulnerabilities database at
securityfocus.com, it found 2
problems with apache (both for 1996) and about 30 security problems with
IIS (most for 1999-2000).
Netscape server (now iPlanet). Runs on about 7.5% of the Web sites.
Have Web interface for configuration. Have some additional features like
publishing, build-in search engine, but it's bigger and uses much more
memory than apache.