Googleand other major search enginesurge you to avoid overly aggressive SEO practices when you build your site. Google has actually taken the trouble to spell out SEO practices it regards as naughty (the list can be found at http://www.google.com/webmasters). You should pay attention to this list as if it speaks the mind of every major search engine, not just Google. Google's position that building sites that get highly ranked is simply a matter of providing useful content isn't totally off-the-wall, although it assumes a world where everything always works.
According to Google, good search-engine-citizen web sites do not:
Employ hidden text or links
For example, users cannot read white text on a white background (and will never even know it is there). But the search engine will still parse this text. This rule comes down to making sure that the search engine sees the same thing that users view.
Also called stealth, this is a technique that involves serving different pages to the search engine than to the user.
Use redirects in a deceptive way
It's easy to redirect the user's browser to another page. If this is done for deceptive purposesfor example, to make a user think they are on a page associated with a well-known brand when in fact they are on a web spammer's pageit's frowned upon.
Attempt to improve your PageRank with dubious schemes
Linking to web spammers or bad neighborhoods on the Web may actually hurt your own PageRank (or search ranking), even if doing so provides inbound links to your site.
Bad neighborhoods are primarily link farms or link exchangessites that exist solely for the purpose of boosting a site's inbound links without other content. Web spammers are sites that disguise themselves with pseudo descriptions and fake keywordsthe descriptions and keywords do not truly represent what the site contains.
Practice keyword loading
This is the practice, beloved by SEO "experts," of adding irrelevant words to pages (the page can then be served as the search result based on a query for the irrelevant words that actually don't have anything to do with the page content). Proper keyword usage highlights your legitimate content but does keyword load.
Create multiple similar pages
Google frowns on the creation of pages, domains, and subdomains that duplicate contentalthough obviously there are places to legitimately duplicate content.
Present "doorway" pages
Pages created just for search engines are sometimes called doorway pages. (The term doorway page covers a variety of techniques that are used to substitute one page for anothereither by redirection or actual substitution of pages on the web serverwhen the first page is optimized for specific keyword searches, and the page to which the user is actually sent has little or nothing to do with that search.)
Pages that lack content
Google frowns pages that lack original content, such as a page that exists simply to present affiliate links.
Create domains with the intention of confusing users
Likely you've landed on a site with a domain name that's confusing because it's sharing the same name with a different domain suffix (for example, http://www.php.org, which combines a redirection with the deception, rather than the legitimate PHP language site, http://www.php.net), or because of a slight spelling variation (http://www.yahho.com rather than http://www.yahoo.com, http://www.goggle.com instead of http://www.google.com).