When friendly is not friendly

Internet Explorer introduced “Friendly HTTP Error Messages” for certain HTTP errors (400, 403, 404, 405, 406, 408, 409, 410, 500, 501, 505). For instance if your ASP page does something bad that results in HTTP 500 error, IE will typically display a friendly message to the user, which looks something like this:



Additionally, the error message might contain other information that was generated by the offending page. If the error message produced by your page is more than 512 bytes (the thresholds are stored in the key HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer\Main\ErrorThreshold) then IE does not show the friendly error page but the entire output from the webserver as it is. Which is why you might not get these friendly messages when woking with ASP.NET; given the verbose nature of error messages generated by them.

Friendly or not, as a web developer, IE’s substituted messages might come in the way of debugging your page. They can be disabled from Tools -> Internet Options -> Advanced:



I use the cluster of 3 radio-buttons (Underline Links) as a landmark to quickly locate the right checkbox in this crowd of checkboxes.