Understanding linking and link popularity is crucial for achieving high search engine rankings -- and for avoiding penalties for abusing the often-times unspoken rules.
1). Want to know when another site has linked to your site? You can build a basic free link alert service using a tool like TrackEngine.com and the reverse link search feature of your favorite search engine.
2). A link to your site that search engines do not know about is worthless from the standpoint of link popularity, but can still be a very important link nonetheless. Not all people will use a search engine on the way to your site.
3). Whether the search engines ever work out the kinks with link popularity measurements, if you have built a nice network of links pointing at your site, you will still benefit from surfers' discovering you.
4). Not all links are created equal. A link to your site from a major directory like Yahoo is often seen as far more valuable than a link to your site from the personal home page your kid built at GeoCities.
5). Free-For-All (FFA) links pages and link farms have zero effect on link popularity, and more importantly, will not send you a single qualified visitor. Stop feeding them. They encourage spam.
6). Since most search engines don't spider beyond the second or third level of any site level, they'll never know about a link to your site if that link exists deeper than the engine crawls. This means deep links can't factor into link popularity measurements unless the crawler knows about them.
7). It is never appropriate to submit someone else's URLs to the search engines unless they have given you permission to do so. If you find a site with a link to your site, don't submit it just because you want to make sure the engine knows abut it. This discourages linking.
8). We often overlook a simple yet effective way to encourage links: A detailed link instructions page. Most sites have several different ways they can be linked to. A simple text link, a graphical link via button or badge. A unique URL link. If your site offers a searchable database of some sort, there's a search box link. But how to you help other webmasters to know just how you'd like those links to appear? Tell them using a link instructions page.
9). For content sites, the biggest missed opportunity I see from a linking perspective is focusing only on the site's main URL, or home page. Depending on your site's content and features, you may have many linkable content elements beyond your home page URL. E-Newsletters, E-Zines, PDF Files, Images, Software, Sweepstakes, Web cams -- all of these can be linked and submitted to topical search engines and directories, aside from the regular text homepage.
10). Both the Netscape and Internet Explorer Web browsers have "Recommended Sites" buttons that will examine the site you are on and recommend others like it. Alexa powers this. So go get your site linked/indexed by Alexa. It's free.
11). There is a battle going on concerning dead dot-com site links. Good sites that were around for a few years had built up a nice collection of links pointing to them. Then the crash happened, and content couldn't pay for itself. When these sites went belly up the porn sites re-registered the domains and captured the one remaining asset those sites had: link equity. Don't let this happen to you. Spend a few dollars to keep up a single homepage at your now-defunct site and redirect the traffic to a worthy cause.
Eric Ward founded the Web's first service for announcing and linking Web sites back in 1994, and he still offers those services today. He's the editor of LinkAlert! and founder, NetPOST, URLwire, and LinkPlan, and also writes columns for ClickZ and Ad Age magazine. More information on Eric: http://www.ericward.com/linkalert/ or contact him at email@example.com
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