What search engines don't like
Don't do it!
It is extremely important to know what search engines don't want. Otherwise, your perfectly optimised site may not be indexed -- and could even be blacklisted. Therefore, when you learn about factors that influence search engine rankings, you should also learn which tactics to avoid.

Spam - search engines' worst enemy
Search engines hate tactics intended to fool them into awarding high rankings to irrelevant pages. These tactics are called "spam." Search engines strive to provide the most relevant results to their users, but spam clutters their indices with irrelevant information.

Some webmasters create spam after they learn which criteria search engines use to rank pages. For example, search engines give high scores to pages filled with keywords. Webmasters came up with a way to add more keywords without sacrificing a site's appearance. They use invisible text ( the background and the text are the same colour, so the text is not seen by the visitor). Previously, robots that indexed invisible keywords ranked those sites higher for keyword frequency and weight.

Search engines now know of this technique and define it as spam. Currently, sites that use invisible text are banned from most of the major search engines.

The following techniques are usually considered spam:

• Meta refresh tags
• Invisible text and overuse of tiny text
• Irrelevant keywords in the title and meta tags
• Excessive repetition of keywords
• Overuse of mirror sites (same sites that point to different URL's)
  Submitting too many pages in one day
• Identical or nearly identical pages
• Submitting to an inappropriate category (for directories)
• Link farms

Frames, dynamic content and Flash intros
Although search engines won't penalize for the use of frames, dynamic content and multimedia files, they will have difficulty indexing them.

Recently, some engines started to index dynamic content. However, most search engines are still unable to index multimedia and dynamic pages, and those that are, don't index all of them. Here's a list of files that search engines don't index:

• Text in graphics (use ALT tags instead)
• Pages that require registration, cookies or passwords
• XML
• Java applets
• Acrobat files (PDF), except Google
• Dynamic content (URLs with "?" in them), except Google, Altavista, FAST and Inktomi
• Multimedia files (Flash, Shockwave, streaming video)