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Links to enhance the weight of the site has a very big help, and one-way friendship link effect is better, because of this, there are a lot of webmaster trying to get through the "unknown" means to obtain one-way links, the following to introduce what the means.
First: JS call
Use JS to call the link bar displayed in the Web page, although from the surface of the site is shown on the link, but the link to this form of the call is not crawled by search engine crawler, generally cheat novice webmaster easier, because many novice webmaster even see the source code do not understand.
Solution: After the successful exchange of links with the other party, open the source code of the other site, and then enter their own domain name in the query bar, see whether there is a display, if no hint should be detailed inspection, whether the use of "unknown" means.
Second: nofollow label
This label means to tell the search engine crawler, this link does not need to pass the weight, so when the search engine crawler crawl site content, will add a nofollow tag link blocked off, in fact, many webmasters do not understand the meaning of the label, so this "unknown" means more common.
Solution: Open the source code of the other site, in the search field input "Nofollow" for search, such as the appearance of the label, to see whether to screen the daily Friendship link address, if so, do not recommend to exchange links with such stations.
Third: The IFRAME code
This code is a bit like the use of JS calls, on the surface of the site appears to be very normal, but when viewing the source code of the site, it is not displayed links.
Solution: Open the other side of the site source code, see whether the Friendship link use the IFRAME codes call, if it is not to exchange with such sites, because it is not any weight transmission.
IV: Delete at any time
A lot of black-hearted webmaster in the exchange of links after the second day of the link to remove it, so that the search engine crawler is mistaken for one-way links, give a higher weight.
Solution: only diligent daily check friendship link situation can effectively avoid this phenomenon.
The above four kinds are more common "unknown" cheating means, of course, do not rule out some higher technical content of cheating means, but as long as in the exchange of links when the attention of the above four kinds, basically can effectively avoid falling into the trap of the black-hearted webmaster.
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