Tools for checking HTTP requests and responses from a server are required for your web server’s response to a particular request.
Tools for checking HTTP requests and responses from a server : FireFox Plugin
Firebug must be listed among the free tools for checking HTTP requests and responses from a server. From the network monitor in Firebug you can see all the requests made by loading the current page, the total time and total size of all elements on your back and the headers sent and received, status codes and time response to each request.

YSlow and FireCookie as Addons in Firefox:
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If you are using Firebug and other FF Addons as tools for checking HTTP requests, it is recommended to use FireCookie and YSlow as additional tools.
Free Online Tools for checking HTTP requests and responses from a server
Web-Sniffer: Very old and well known among the free tools for checking HTTP requests and responses from a server.
Rex Swain’s HTTP Viewer : Another mentionable tool among the tools for checking HTTP requests.
Check HTTP Header : Like other tools for checking HTTP requests, it serves the same purpose plus shows the meta descriptions.
With this list of tools for checking HTTP requests, you should be able to check the HTTP headers and status codes that your web server responds to a particular request.
