View the source of each and every page: is there JavaScript and CSS on the page? Remember that spiders may not index pages that have more than 10k or so of JavaScript or CSS embedded in them. Spiders dont enjoy getting tangled up in JavaScript. So as a general rule you should avoid putting out prompts and alerts using JavaScript every time that a page loads. Because of this rule, it is also wise to avoid link partners who do so on the pages that they link to you from. If anything looks fishy, it probably is.

CSS wont give you many problems. If you are going to use CSS, it is best to link to it from another source. Create a separate CSS page and use the tag to work it into the head of your HTML. This method will keep your file size down considerably, and since you will probably be using the same CSS on several pages, decrease your bandwidth usage. Normally a large quantity of CSS within the document isnt indicative of any suspicious behavior on the part of the linker. If you feel that you are, indeed, suffering from the fact that the site uses such an excessive proportion of CSS on the page itself, suggest to the webmaster that he/she may want to create an external CSS document and link to it in his/her header.

Check that you're still on the domain you clicked on a link to, and you haven't moved to another site or a subdomain. Some people will move you to another domain while telling thats their site and your link is there, relying on you not checking the address bar. This trick is all too common and happens to folks who are new to SEO every single day. This sad fact will continue until people begin to catch it every time.

If the domain has changed, delete your backlink to the site in question immediately and then email the webmaster with your complaint. If the webmaster does not fix the problem you may even want to request that they remove the link as the site may wind up discredited as a link farm or some such thing that you do not want to be associated with for fear of being banned from many popular search engines with technology used to combat link farms.

On a related subject, when you check your back links, make sure that these links appear in legitimate places. If the site is completely dedicated to linking to other sites and doesnt seem to be a directory or something similar you will want to get your link removed as soon as possible. There is no time when one link is worth the risk of being permanently banned from any popular search engine. Aside from the traffic that you will lose from that one search engine, you may wind up red flagged so to speak. It seems to be common practice among search engines that if one finds faulty activity the rest seem to find out soon afterwards.

Overall, if it seems dodgy, leave it alone. Its better to sacrifice one link in caution than to destroy your sites rankings by accepting one youre not sure of. There are hundreds of situations aside from link farms that can and will give you trouble. It would be impossible to list every scam as there are people who make their living (or seem to anyway) in creating and executing these scams. Whenever there is a new form of SEO technology that cant fail, you should watch out because it is almost guaranteed to blow up in your face. The only truly powerful and guaranteed method of SEO is to make your site valuable to your visitors and then let it fall where it may in the realm of the search engine.

It is difficult, after you have optimized your pages and submitted them to search engines and directories, to sit back and wait, but there is not much that can be done aside from attempting to accumulate links from good, solid places. The work that you have done is bound to pay off sooner or later as long as you stay honest. When it comes to the world of SEO, honesty is, indeed, the best policy.