GZip & Hostgator
via php.ini
At the time of writing (March 2010), hostgator does not enable gzip compression on pages via apache if you are on a shared server (resellers included) - Which we all have issues with...
First of all, here's a good website that can check whether http compression is being used:
http://www.whatsmyip.org/http_compression/
You may have tried using htaccess to utilise mod_gzip or mod_deflate without success. Well here is another way to compress output at least for php pages of your website. If you aren't using a php page, then there will be no compression.
In your php.ini file (possibly located before public_html folder), find the line 'output_handler'. Remove the semi-colon and after the equals sign put in 'ob_gzhandler' like so: output_handler = ob_gzhandler
After you have done this, any php pages will have output compression applied to them. Check back with http://www.whatsmyip.org/http_compression/ and it will show you the difference.