May 20th, 2003 Update: Matt Cutts, a Google representative, put out a warning at a recent search engine conference in Boston that Google will be cracking down on hidden text and invisible pixel images. Since Google already has the technology to index images, such a threat should carry some weight. You'd be wise to avoid typical methods to hide text and links if you wish to be safe with Google. Rather than hiding links, consider creating a site map page that links to your other important pages without using the transparent pixel technique. We'll report more on this as information becomes available.
First and foremost, it's best to avoid hidden links in the first place to eliminate any chance of you being labeled as a "spammer" by a search engine. Most engines state they do not like hidden text, or perhaps more accurately, improperly hidden text. Therefore, the question is does this also apply to links? Although most engines say nothing about this subject, Google has stated on their site that they dislike both hidden text AND hidden links.
In reality, some types of hidden TEXT are completely acceptable. For example, keywords in your meta tags are hidden from the user's view but visible to many search engines. Other areas like ALT tags and the NOFRAMES area are also hidden from the user's view but are NOT considered to be spam by any search engines. However, if you include keywords in these hidden areas that do NOT apply to the visible content of the page, you have now crossed over into the realm of spam. Ultimately, the search engines want to index the same thing that the user sees which is why they don't like to index redirected or cloaked pages. In the case of a cloaked page, ALL the content is hidden in that one page is served to the search engine and another page is served to the user.
There are reasons a Webmaster may wish to hide a link from the end user but allow a search engine to find it. For example, you may have a list of pages that you feel are important that you want to ensure the search engine sees. However, if these pages are several links down from the home page, the search engine may never spider down far enough to find it. You could add links to your home page but too many links on the home page can often create a confusing user interface for the Web visitor. A solution used by many to this and similar problems is to create links that the search engine will see but the average visitor will not.
You may be asking "why do I need links that travel from my home page to arrive at my other search engine optimized pages? I could simply submit them directly right?" That's true, but many engines give additional relevance to pages that it finds on its own rather than having been submitted directly. In addition, some engines like to see a path from the home page to any other page it indexes. If it does not, it may penalize that page or drop it from its index. At the very least, the page may be more likely to be dropped by an engine at a later date if it doesn't find it each time it spiders your site.
So, if you wish the links to some of your pages to be hidden to the user but to be visible to the search engines, you'd submit your home page or another page which includes image links such as the following:
<A HREF="myoptimizedpage.htm"><IMG SRC="myimage.gif" ALT="mykeywords" BORDER="0"></A>
Note that the height and width tags were intentionally left out. It's possible that an engine may decide in the future to not spider links from images that are known to be only one pixel in size. Without those tags, the engine cannot easily determine the size of the graphic, so you eliminate that possible risk. Since the image is only 1 pixel in size, it is almost impossible for a user to notice unless the mouse cursor is very close to it.
Note that the ALT tag above is optional. However, you may want to include a description of the link that includes your important keywords. Some engines could choose to use them in evaluating the keyword relevancy of the page you link to, or for the page they are placed on.
The "myimage.gif" file in the above example would be a small GIF or JPG image that does not appear clickable to the average user. In the past, Webmasters have used transparent GIFs to hide links and done so with great success. However, it's almost a certainty that with more recent policy changes, that Google will be scanning for hyper-linked image files that are entirely transparent. They could then choose to ignore such links or even to penalize the page or Web site. Some people argue that you could use a larger GIF or JPG image the size of a small button, containing non-transparent colors, that simply does not scream "click me." For example, there are many ways to integrate an image into other artwork or background elements on the Web site without making it the exact same color, or truly hidden. These same people argue that there are necessary uses for hidden image links. For example, if you use a java script or other menu system on your page that does not have simple HREF links that search engines can follow, you need to provide SOMETHING for them to spider. Therefore, they argue that even if search engines can detect hidden links, why would they want to? The image links provide a service to the search engines by pointing them to valuable content they might otherwise miss.
Some of the largest, most popular Web sites on the Web have home pages with menu systems that most search engines cannot navigate. Therefore, an argument can be made that you can use these type of links without fear of problems from the engines. The same argument cannot be made as strongly for hidden text.
An alternative to the hidden image method is the hidden text link. Hidden text links are closely related to the technique of hiding keywords in invisible text that we've discouraged for years. WebPosition will red flag your page in the Critic report if it detects invisible text created through the use of setting the same color text as the background. This is a big "no no" since it can get your page dropped from many search engines. Some Webmasters will vary the color code just enough to keep it from being visible to the naked eye, but to ensure it looks visible to a search engine.
One concern by the search engines is that you're going to hide keywords that are not relevant to the page in those hidden areas. The user would then wonder why XYZ engine ranked the page so favorably for their search when they don't even see the keyword on the page.
Some Web marketers will place keywords in hidden TEXT links to boost the relevance of the pages. For example, Google will rank a page higher for "Keyword X" if it sees many links pointing to a page using "Keyword X" in the link text. Since Google's algorithm relies heavily on what keywords are found in the normally visible link text, they are more apt to try to ban a page employing such a technique.
In conclusion, we'd encourage you to avoid hiding text or text links by setting the colors of the font and background the same. In the case of using hidden images with links to enhance navigation for search engine spiders, we'll leave that up to you to decide based on your particular situation. Many people find that they can avoid the use of hidden links, and thus any controversy, by creating a "site map" page. This site map will contain visible links to all their important pages. The site map page is then linked to from the home page, placing all their important pages within two "jumps" of the home page. Many large sites include site maps organized by topic. Even Google includes a site map page. Unfortunately, site maps have their limits too. Industry experts suggest that you avoid using more than 50 links on a single page to avoid some of those links from being ignored on some engines.
