Preventing Duplicate Results in Web Pages and Mobile Web Pages


Posted by Sam Battin, Senior Search Strategist

How do you keep your site’s mobile Web pages out of regular search results?

You may have seen this happen–based on the recommendation of your head of marketing–you set up a mobile version of your website.  This way, people who are browsing the Web from their iPhone, BlackBerry or other mobile phone can visit your site and see pages formatted for a small screen.  People who browse the Web from a PC or a laptop will still see the regular site.  At first, this works out great, because you’re reaching a whole new strata of potential customers.

After a while, however, you find out that your mobile site’s Web pages were appearing in the regular search results!  If a consumer looked for your company in a search engine, they might find a link to your normal site or to your mobile site, and you couldn’t control which one!  You even found out that your site was getting penalized for duplicate content!  Your head of marketing claims to know nothing about this!  What do you do?

In the Natural Search Department at Performics, we see this kind of thing all the time, and we’d like to let you know there’s an easy, easy fix for this.  Even your head of marketing will be able to tell whether the IT department did it right.

There’s a little line of code at the very top of most Web pages.  This line of code says what version of HTML the page is using.  Browsers and search engines use this line of code to figure out how to render and/or display the page they’re looking at.  This line of code is called a DOCTYPE declaration because it makes a

DECLARATION about the
TYPE of
DOC-ument you’re looking at. 

Here’s a DOCTYPE for a standard Web page meant to be viewed from a PC or laptop:

<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd”>

Translated, the above code means that the Web page is using the “transitional” form of XHTML version 1.0, and it contains a link to the complete specifications for this language.

Search engines aren’t dummies.  They know that the mobile version of your site is probably going to have the same information as the regular version of your site. They don’t want duplicate results from the two versions of your site contaminating their search result pages.  They also don’t want mobile users to click links that take them to regular Web pages; this would produce a bad user experience, and people might stop using their search engine. 

For these reasons, search engines take it easy on webmasters with mobile sites.  Just use the right DOCTYPE and all your duplicate content problems will be solved.

Pages on your mobile site should have their own DOCTYPE declaration.  If your IT department did a good job, the pages on your mobile site should have a DOCTYPE like the following:

<!DOCTYPE html PUBLIC “-//WAPFORUM//DTD XHTML Mobile 1.0//EN”  “http://www.wapforum.org/DTD/xhtml-mobile10.dtd”>

Translated, the above code means the Web page is written in the 1.0 version of XHTML, specifically written for mobile Web pages.

This is all you need (and that’s all search engines need) to make sure your regular and mobile sites aren’t going to interfere with each other on search engine result pages. 

A search engine robot who visits a mobile Web page and sees that the page has a mobile DOCTYPE will say “Oh – this page is for mobile phones.  Therefore, I will make sure this URL only appears for people who do searches from a mobile phone.”

Sadly, there are still some companies out there who built a mobile site that didn’t include the correct DOCTYPE declaration.  Search engines visit their mobile site and they don’t know that it’s a mobile site.  As a result, search engines are finding tons of duplicate content and users are clicking on the wrong version of the page, having a bad experience, and leaving your site.

Don’t let this happen to you.  Go to your mobile site and view the source code of the page.  It should have a mobile DOCTYPE declaration.  If it doesn’t, you should have a word with your IT department.  They should be able to fix it, and get your site back on track.


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