There's a tiny http daemon server that I use for this sort of thing.  I've never heard that you can configure any of the browsers to execute script for you, so you're probably stuck with a similar setup to mine:
You can find shttpd (now called mongoose, from the looks of it) at sourceforge.  The config file I use for my ruby apps looks like this:
# SHTTPD web server configuration file.
# Lines starting with '#' and empty lines are ignored.
# For detailed description, visit http://shttpd.sourceforge.net/shttpd.1.txt
#platform-specific stuff
root            c:\main\src\worker\http
systray         no
access_log      logs\shttpd_access_log.txt
error_log       logs\shttpd_error_log.txt
cgi_env         RUBYLIB=c:\main\src\worker;c:\main\src\worker\lib
cgi_interp      c:\InstantRails\ruby\bin\ruby.exe
#platform-dependant stuff
ports           2001
cgi_ext         rb
threads         5
index_files     index.rb
If you have any further questions, just update and I'll try to keep an eye on the thread.