To test the compression of items in a web page we can use firebug to test individual items. Open firebug and go to Net tab. There you’ll find all the elements of the page. Expand any element and check “Response Header”. There will be so many entries as below:
style.css
Date Tue, 13 Dec 2011 05:44:53 GMT
Server Apache
Last-Modified Wed, 03 Aug 2011 17:53:37 GMT
Etag “2f8c09f-3ae2-4e398b21″
Content-Encoding gzip
Accept-Ranges bytes
Content-Length 15074
Keep-Alive timeout=5, max=100
Connection Keep-Alive
Content-Type text/css
Group wise items can also be selected by using the sub tabs like html,css, js etc. XHR tab is for ajax requests. There you can check all the requests which are made dynamically using ajax.
Here look for “Content-Encoding” if it says gzip then the item is compressed. Now it is good to serve text items like the page itself (html, jsp, aspx etc), css, javascript etc as compressed items. This saves bandwidth and serves the page quickly.