If you’re involved in the testing process for a web application and you use Internet Explorer for testing, one of the first things that you will need to do is to turn off “friendly HTTP error messages”. This option is turned on by default and I can understand why Microsoft did it because most people are ordinary consumers who won’t be bothered with deciphering the error messages that the server throws back.
Turning this option off will display the error message returned from the server in all its techno-geek glory that only IT people can decipher. Incidentally, these error messages are also often useful when testing. For instance, Weblogic Server Developer License only allows 5 unique IP addresses and it will inform you via the error message if you should exceed that. However, if friendly HTTP is on, you will only know that access has been denied without knowing the reason.
If you have trouble finding this option in your IE options, I’ve reproduced a screenshot below.