Add to http.conf this:

1. 1. 1. Page compression
         <IfModule mod_deflate.c>
         AddOutputFilterByType DEFLATE text/plain text/html text/xml text/css text/javascript
         AddOutputFilterByType DEFLATE application/xml application/xhtml+xml application/rss+xml application/javascript application/x-javascript

BrowserMatch ^Mozilla/4 gzip-only-text/html
BrowserMatch ^Mozilla/4\.0[678] no-gzip
BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
</IfModule>

Turn off any gzip compression at application layer (Clearspace, magnolia etc.)