Sencillo código sin tener que editar la configuración de apache:
<IfModule mod_deflate.c> AddOutputFilterByType DEFLATE text/css text/x-component application/x-javascript application/javascript text/javascript text/x-js text/html text/richtext image/svg+xml text/plain text/xsd text/xsl text/xml image/x-icon application/json </IfModule>
Otra variante:
<IfModule mod_deflate.c> BrowserMatch ^Mozilla/4 gzip-only-text/html BrowserMatch ^Mozilla/4.0[678] no-gzip BrowserMatch bMSIE !no-gzip !gzip-only-text/html AddOutputFilterByType DEFLATE text/plain AddOutputFilterByType DEFLATE text/xml AddOutputFilterByType DEFLATE application/xhtml+xml AddOutputFilterByType DEFLATE text/css AddOutputFilterByType DEFLATE application/xml AddOutputFilterByType DEFLATE image/svg+xml AddOutputFilterByType DEFLATE application/rss+xml AddOutputFilterByType DEFLATE application/atom_xml AddOutputFilterByType DEFLATE application/x-javascript AddOutputFilterByType DEFLATE application/x-httpd-php AddOutputFilterByType DEFLATE application/x-httpd-fastphp AddOutputFilterByType DEFLATE application/x-httpd-eruby AddOutputFilterByType DEFLATE text/html </IfModule>
Si da error 500 lo quitan, seguramente sea por que mod_deflate no este habilitado.
Con eso comprimimos todo el contenido, mod page speed de google nos nos dará el error, aceleramos la carga y reducimos el consumo de ancho de banda.