I've been asked quite a few times recently about various factors that affect a site's ranking in the search engines. Invariably, most people I talk with aren't familiar with Google's published best practices for Search Engine Optimization (SEO). Their online guide is quite useful for familiarizing (or re-familiarizing) yourself with the basics. In this post, I'll specifically highlight a few of the points in that guide based on questions I've recently been asked by clients and conference attendees.
"404 Not Founds Don't Affect Search Ranking, Right?"
Directly affect search? No. According to Google's help documentation on error pages:
That word generally seems to linger there, almost taunting you with a false sense of security. Generally it certainly doesn't imply any commodum of absoluteness. Sure, it's likely it won't affect your rankings, but there's always that chance.
Google's Webmaster Tools have a slightly different message regarding 404 errors:
That same word - generally - is still in effect. But the Google Webmaster Tools team suggests you can use 404s to help improve the user experience. This leads us to a great segue to the next commonly asked question.
"Does Google Use My Site's Bounce Rate Against Me in Rankings?"
Simply put, no. Until Google gives us a real reason to think they have conflicting policies, then we go by what they say. Google Analytics (which measures bounce rate) does not share its data with other Google products unless you let it. Google does have a pseudo-bounce rate signal which does carry some negative weight. However, that bounce rate is calculated quite differently than what your Google Analytics tracks and measures.
About two years ago, Google made a series of changes to search. One of them allowed users to block sites they never wanted to see in a future Google search result. This feature is triggered by how much time you spend on a site before clicking back to the Google result page. If you stayed on for an undisclosed number of seconds or less, the block message and link would appear.
Around this same time, Google also announced that bounce rates would be considered a signal in rankings. However, if we believe Google Analytics won't bleed this data through to Search without our permission, then we can only conclude that Google would calculate that bounce rate differently. Presumably, through the same method that they used to ask users if a site was not worthy to be seen in results.
Putting it All Together...
If I find your site via a Google search, but land on a page that gives me a 404 error and I immediately click back to Google's result page, they will undoubtedly know about it. They'll also know how long (little!) I spent on your site. If that happens too many times, you can bet your bottom dollar that Google will start to seriously take note. Indirectly, the user experience generated from finding a 404 (especially on the first page) would have an impact on that user's decision to return to Google and generate some sort of signal.
Look through your Google Webmaster Tools reports to see if Google has a lot of 404s listed for your site. Did you recently redesign and forget to redirect old URLs to the new ones? Don't let 404 errors ruin your users' experience. The SEOQuake toolbar makes it extremely quick and easy to see how many pages each search engine has indexed for your domain. If that number is considerably higher than the number of pages you know you have on your site, there's a chance a 404 can come up in a search result.