Hidden text & links
The act of making the text the same colour as the background, people seem to think that the search engines are dim enough to over look white text on a white back ground. This one is as old as they come and the search engines are aware of it. Sites may rank using these methods for a while as it can take a little while for the engines to catch up with them. The same goes for white text links on a white back ground! People have now taken to hiding text and links behind invisable CSS divs and even using the Z index to hide the text off the page
Double tags
Duplicate title tags, duplicate Meta tags are an old trick that again do not give any real boosts in the search engines.
Cloaking
The art of delivering the search engine one page and giving the user a different page. For the best effect the server will scan the IP address of the incoming connection to the web server. If it matches an IP address that is known to belong to a search engine it will get a text rich page with heavily descriptive title tags, Meta tags and text copy. If the next IP address is not recognised it must belong to a user, if so the server will deliver it a normal page – with graphics etc… If cloaking is done correctly it is undetectable, the search engines will continue to get the text heavy pages while the normal visitors get the nice looking graphics site.
Poor mans cloaking is looking for the user agent string and then delivering content based on that alone, this is really easy to detect as it is simple to spoof your user agent and then detect the cloaking.
Blog & Wiki spamming
As you know search engines place great importance on links (if not where have you been for the last 18 months) that point to your website, so much so that people will place their text links anywhere just to increase their backlink count. Blogs are sites enable site owners to easily post their thoughts to as it is all done with a content management system. One of the unique selling points of a blog is that it lets any person comment to the site, it enables you to have a full and open discussion about any topic in such a way that has never been seen before. With the openness of a blog you may leave yourself wide open to blog spammers, people who run automated crawlers who hunt out blogs and then post keyworded text links, these guys dont just hit a few a day – we are talking hundreds of thousands maybe even millions. These sorts of tactics are live fast die young, as the search engines can close down the benefits of the links maybe with in a few months and then eventually knock out the domain the links are pointing to. There are a few things that are out there to stop the blog spammers but all seem to be falling short – spammers hit the blogs that are old and not updated any more and hit thousands at a time.
Wiki’s are sites that will let anyone add or update the content of any page on the site, great for adding links to! Some people say the knew choice of blog spammers.
Hijacking/pagejacking
The latest and nastiest of spamming there currently is. The way that Google currently reads 302 redirects has a slight fault in it, if a page that has a 302 redirect to another site of a lower PR there is every chance that the page doing the redirecting will start to rank for the other pages keyphrases dependant on several other factors. I dont want to go into to much detail on this one, dont want any more hijackers out there than there already are ;o) Webmasterworld pagejacking thread