This is the support thread for .htaccess Optimisation.
Installation:
Upload the .htaccess file, or if you already have one, copy the text and add it to your .htaccess file.
What does it do?
This add-on will optimise your site, massively speeding it up, reducing your bandwidth usage and possibly increase your search engine ranking.
How?
In two ways, first, by compressing files that can be sent compressed, sometimes reducing file transfer size by upto 80%. Second, by controlling the cache, thus again reducing server load.
Link: http://addons.oscommerce.com/info/8927