On to Apache configuration
By default, Apache comes preconfigured to serve a maximum of 256 clients simultaneously. This particular configuration setting can be found in the file /etc/httpd/conf/httpd.conf (though the location of the file may vary, depending on the Linux distribution you use).
Whip your favorite text editor out and open that file (remember that you should be doing this as root — the administrative account on the majority of Linux servers out there).
Look for MaxClients. It will probably look like this:
# prefork MPM