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HTTP error code troubleshooting, Part 3: Disabling IE friendly error messages

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More on HTTP error code troubleshooting
Part 1: What each series of HTTP error status codes means
Part 2: How to use WFetch to troubleshoot HTTP error codes
Part 3: Disabling friendly error messages to find root problems

So far in this article series, I have shown you a few different methods for getting to the bottom of an HTTP error message. In this article, I want to conclude the series by showing you one last technique for dealing with an HTTP error message.

Friendly errors
One reason why HTTP errors are so hard to troubleshoot is that Microsoft likes to hide a lot of the details about the error message from us. I don't think that this information is being obscured for security reasons or because Microsoft wants to withhold information from us; rather, it seems to be an effort to help people who are less computer literate.

For example, one of the most common types of HTTP error message is the 404 error. To see what a 404 error looks like, just go to your favorite website and enter an invalid URL. When you do, you will most likely see an error message like the one that is displayed in Figure A.

Figure A
A 404 error is one of the most common types of HTTP errors.

Click the image for a larger view.

As you can see in the figure, the fine print tells you that a 404 error has occurred, and it even tells you that the error occurred because a file was not found. That's really about the only technical information we get, though. The rest of the information on the page is there to tell novices how they might be able to get around the error message.

Sometimes friendly error messages are dressed up a bit. For example, if you go to my website (www.brienposey.com) and enter an invalid URL, you will see a page similar to the one shown in Figure B. This is still considered a friendly error message. I have simply replaced Microsoft's generic error message with a message of my own. Many other sites use the same technique.

Figure B
Some websites use custom friendly errors.

Click the image for a larger view.

Whether a site uses a generic or custom friendly error message, you probably won't get a lot of technical information about the problem from it. Fortunately, there is something you can do. Internet Explorer contains an option that you can use to display the real error message instead of the friendly error message.

The exact method of doing this varies from one version of Internet Explorer to another, but here's how it's done in Internet Explorer 7. Choose the Internet Options command from the Tools menu. When Windows displays the Internet Options properties sheet, go to the properties sheet's Advanced tab. Finally, deselect the Show Friendly HTTP Error Messages check box, located in the Browsing section. When you're done, click OK.

When disabling friendly error messages does nothing
After you disable the friendly HTTP error messages, you may find that the error pages still look the same. A couple of things can cause this. For starters, if you are looking at a 404 error, the error message is typically going to look the same because there really isn't anything to report except that the requested file was not found.

Another reason why an error may not look any different than before is that Internet Explorer may not actually be making a connection to the website. For example, if your Internet connection is down, you will get a 404 error message whether the page you requested actually exists or not.

Another common reason for continuing to receive generic error messages is that the requested page may be cached. Try emptying the browser cache and then requesting the page again.

If you own the website that is having problems and that website is running on IIS 7, try accessing the site locally, directly from the server console. Doing so will ensure that you receive a detailed error message. If a site is coded using ASP.net, you may end up receiving ASP's custom errors instead of the detailed messages that you are interested in. If this happens, you can fix the problem by temporarily embedding the following code onto the page that you are troubleshooting:

‹system.web›
‹custom errors mode="Off" /›
‹/system.web›

Conclusion
In this article, I have explained how you can disable Internet Explorer's friendly error messages. I then went on to talk about a couple of reasons why you may continue to see friendly error messages even when you have disabled friendly error messages in your browser.

Brien M. Posey

About the author:
Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server and IIS. Brien has served as CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. As a freelance technical writer, he has written for Microsoft, CNET, ZDNet, TechTarget, MSD2D, Relevant Technologies and other technology companies. You can visit Brien's personal website at www.brienposey.com.


 

This was first published in December 2008

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