making a correction here to be more specific.

I guess i'm looking for a GZIP compression tool for web pages. (I didn't even know webpages will still load if their GZIP'd. will they ? )

results when running optimizer from webpagetest.org -

GZIP encode all appropriate text assets (text responses > 1400 bytes):

FAILED (12.6 KB, compressed = 2.5 KB - savings of 10.1 KB) -
FAILED (8.4 KB, compressed = 2.9 KB - savings of 5.5 KB)

[edited by: tedster at 10:11 pm (utc) on Apr 29, 2011]
[edit reason] maintenance [/edit]

the way HTTP compression works is if the user agent is capable of handling gzip-compressed responses, it will send a HTTP Request header similar to "Accept-Encoding: gzip".
most modern user agents support gzip compression.
next, your server should be configured to recognize that header and serve the response document/script/etc in a compressed format only when acceptable.
how this is implemented depends on the server.
if your server is apache it is typically accomplished by installing the mod_gzip module and enabling it in your config or .htaccess.