The three major Web server software vendors :

(1) Apache, the leading Web server software worldwide, is from the Apache Software Foundation, and is an open source project.
Because anyone can afford free, and the software itself is extremely good, it has captured nearly 70% of the web server market, according to Netcaft.com.
Apache is a good choice if you are running Java-based software on your Web server.

(2) Sun. if you are have a Sun Microsystems system running Solaris, which is a UNIX-based operating system that runs Sun servers, you may want to consider using Sun's SunONE web server. This Java-based Web server plays well with other Sun-based products. It only holds about a 3•5% market share, which is a steep drop from its heydays of the mid-to-late-1990s.

(3) Microsoft holds about 25% of the share of the Web server market, Microsoft servers tend to be easier to compromise than Apache servers. Microsoft's Web server is called Internet Information Services 5•0 or 6•0 (IIS 5•0, IIS 6•0), depending on the version you are running.

Hints:
Generally, if you want to run a Java-based architecture or PHP, you should probably run an Apache server.
If you run A.S.P. or •NET, you should run a Microsoft Server.
However, you can run Java-based software using Microsoft-based products, and you can also run Apache on Windows products (since Apache ports its software to multiple operating systems)
If you want to run static HTML pages pick the operating environment you are most comfortable with.