Each time a user agent requests a URL from a website, the server replies with a set of HTTP headers; the requested content follows after them. Most users never see this part of the communication, however, because web browsers do not normally display them.
If you’ve never seen how these headers look, it’s time to get your feet wet. The easiest way to get started is to use a web-based tool that does all of the work for you. One such tool is located at http://www/seoegghead.com/tools/view-http-headers.php.
A more convenient way to view these headers is by using a plugin for your browser. One plugin you can use with Firefox is LiveHTTPHeaders (http://kivehttpheaders.mozdev.org/). For Internet Explorer you can use ieHTTPHeaders (http://www.blunck.se/iehttpheaders/iehttpheaders.html).
The part of the HTTP headers you’re predominantly interested in is the line containing the status code of the request. The most common status code is 200, which specifies the request was processed by your web server successfully without any surprises, and that the content the user requested follows.
However there are many other status code you need to know about, but I’m gonna discuss them in the later articles.
