HTTP Status Analyser
Don't know your 302s from your 301s? Not sure if your error pages are working correctly? This tool analyses the HTTP headers of any webpage. It provides an explanation of the status code that is returned, in addition to the full headers provided by the webpage entered.
New: Now with largely unhelpful, tongue-in-cheek library analogies!
Note: Only HTTP and HTTPS URLS are supported. Friendly explanations are currently available for codes 200, 301, 302, 400, 401, 403, 404, 410, 500 and 503.
Example address bar shortcut for this tool: http://andylangton.co.uk/status/www.example.com