How to Use Server Status Codes for Search Engine Optimization

Part of the Search Engine Optimization All-in-One For Dummies Cheat Sheet

Keeping your server happy and healthy is Job One for a good SEO (search engine optimization) professional. If your site isn't up, your customers can't find you. Use the information in the following table to diagnose problems, sort out redirects, and ensure that everything is working as it should.

Server Status Codes and What They Indicate
Code	Description	Definition	What It Means
200	OK	The Web page appears as expected.	This is what you want to see. Your server and Web page have the welcome mat out for search engine spiders (and users too).
301	Moved Permanently	The Web page has been redirected permanently to another Web page URL.	When a search engine spider sees this status code, it moves easily to the appropriate new page. A 301 Redirect status is NOT a problem for search engine optimization.
302	Found (Moved Temporarily)	The Web page has been moved temporarily to a different URL.	This status should raise a red flag if it’s on your Web server. Even though there are supposed to be legitimate uses for a 302 Redirect code, they can cause serious problems for your optimization efforts. Spammers frequently use 302 Redirects maliciously, so if you don’t want a search engine mistaking your site for a spam site, avoid them.
400	Bad Request	The server could not understand the request because of bad syntax.	This could be caused by a typo in the URL. Whatever the cause, you don’t want a search engine spider blocked from reaching your content pages, so investigate this if you see this status code on your site.
401	Unauthorized	The request requires user authentication.	Usually this means that you need to log in before you can view the page content. Not a good error for spiders to hit.
403	Forbidden	The server understood the request, but refuses to fulfill it.	If you find this status code on your Web site, find out why. If you want to block the spiders from entering, there ought to be a good reason.
404	Not Found	The Web page is not available.	You’ve seen this error code; it’s the “Page Cannot Be Displayed” page that you see when a Web site is down or nonexistent. You definitely do not want a spider following a link to your Web site only to be greeted by a 404 error! That’s like arriving for a party and finding the lights off and the doors locked. If your server check shows you have a 404 error for one of your landing pages, you definitely want to fix it ASAP.
500 and up		Miscellaneous Server Errors	The 500–505 status codes indicate that something’s wrong with your server. Check them out.