Fiddler - Fiddler is a debugging program for websites.
ViewHTTPHeaders.com - View HTTP header response for any web page.
Omnibug - Omnibug is a plugin for the Google Chrome and Mozilla Firefox browsers to ease developing and...
HTTP Header Live - Displays the HTTP header. Edit it and send it.
RequestHeaders.com - HTTP Header Checker Tools
HttpWatch - HttpWatch: The ultimate HTTP Sniffer for Chrome, IE and iOS