At first we probe for a User-Agent string that designates a Netscape Navigator version of 4.x. These versions are not able to handle compression of types apart text/html. The versions 4.06, 4.07 and 4.08 additionally have quandaries with decompressing html files. Thus, we thoroughly turn off the deflate filter for them.
The third BrowserMatch directive fine-tunes the conjectured identity of the User agent, because the Microsoft Internet Explorer identifies itself additionally as "Mozilla/4" but is genuinely able to handle requested compression. Therefore we match against the supplemental string "MSIE" (\b denotes "word boundary") in the User-Agent Header and turn off the restrictions defined afore.
Dealing with proxy servers
The mod_deflate module sends a Vary: Accept-Encoding HTTP response header to vigilant proxies that a cached response should be sent only to clients that send the opportune Accept-Encoding request header. This averts compressed content from being sent to a client that will not understand it.
If some special exclusions are in use which are dependent on say, the User-Agent header, an addition to the Vary header to alert proxies of the additional restrictions must be configured manually. For example, in a typical configuration where the addition of the DEFLATE filter depends on the User-Agent:
Header append Vary User-Agent
Improving page speed
While compressing content by mod_deflate or mod_gzip(in apache 1.3.xx) can improve page speed, others measures can also be taken to improve page speed significantly. Some of the most common used methods are :
Use sprite images : If some images are common across multiple pages such as icons, etc., they should be in sprite format so that all the images can be fetched in a single http request. These images can be managed later on the page by CSS.
Additionally, using compression will further reduce the size again results in improved page speed.