A friend of mine suggested that I would check my site using new Yahoo tool - Yslow to check how my site is performing. One would need to download firebug and YSlow extensions for Firefox.
After performing a mini-audit and about 5 min of searching Google, I've found out that the site could be slightly optimize by adding the following to the htaccess file
ExpiresByType text/css "access plus 4 weeks"
ExpiresByType image/jpeg "access plus 4 weeks"
ExpiresByType image/gif "access plus 4 weeks"
SetOutputFilter DEFLATE - would allow for GZIP compression (http://doc.silverstripe.com/doku.php?id=server-requirements&s=deflate)
FileETag none - would take care of entity tags (ETags) are a mechanism that web servers and browsers use to determine whether the component in the browser's cache matches the one on the origin server.
ExpiresByType - would take care of expires header for given content. You can configure header to expired in any period of time (days, weeks, month, year)
I hope it'll help someone