Countdown script

[Natalie Ford]

I need to put a countdown to a specific date on a web page.  Can anyone 
tell me the best way to do this?  Is there something I have missed in HTML 
itself that will do this?  Do I need JavaScript or Perl or ANOther?  Any 
help will be much appreciated as I need to do this in a relatively short 
time-frame (the next three days?!!)...

Natalie