Never redirect to another domain (AVOID OR GET BANNED)
Redirecting to another domain is not a 100% guarantee that you'll be banned from search engines. But it is a very common spammer trick used in conjunction with doorway pages and cloaking. If you set up a redirect that goes to a new domain, you need to write it as a 301 HTTP redirect, not a 302 or meta refresh. This tells the search engine that this redirect is permanent, and they should change to the new domain in their directory.
Be Careful Redirecting to New Domains - You Could Be Banned
Since this trick is commonly used by spammers, it's a very good idea to avoid doing it. Search engines can be very hard to get back into if your site is banned by mistake.
Never link invisible images (AVOID OR GET BANNED)
Invisible images are images that are 1x1 pixels in size and cannot be seen by the naked eye on a Web page. Since links are given some priority in ranking a Web page, linking images that cannot be seen by your customers appears to be aimed only at search engine spiders.
Don't Link Single Pixel Images - Your Site Will Be Banned
This is similar to hiding text or displaying different content to search engines than to your customers. And don't assume that search engines can't read CSS or HTML tags that resize full-sized images. If you do this to optimize your pages, your site will be banned.
Never include invisible text on your pages (AVOID OR GET BANNED)
Hiding text by making it the same color as the background color may fool your customers, but it won't fool search engines. Another variation of this is where you make the font size so small that it's unreadable by the naked eye.
Don't Hide Text - Your Site Will Be Banned
Search engines understand CSS and font and background colors. They also recognize that a font-size of 1px is not going to be readable. Text that is hidden from your readers but visible to search engines is considered spam and will get your site banned.
Never create doorway pages (AVOID OR GET BANNED)
Doorway pages are very simple HTML pages that are written to optimize heavily on one or two keywords or keyword phrases. And they are programmed so that search engines spiders see them, but regular readers are taken to the real site.
Don't Use Doorway Pages - Your Site Will Be Banned
Doorway pages are designed to trick search engines into thinking that the site has a specific keyword relevance that it may or may not have and they are pages meant to be seen only by the search engine. So, most search engines will ban sites from their directory when they discover you use them.
Never display different content to a spider than customers (AVOID OR GET BANNED)
This is often called cloaking because it is an effort to cloak what your site delivers in something that might be seen as more palatable to search engines. It can be very tempting to use cloaking, but while it might give you better results at first, search engines don't like it.
Don't Cloak Websites - Your Site Will Be Banned
Search engines want to provide a resource of information that is real, not something that has been doctored to give artificial results. When they discover that your site is cloaking, it will be removed from the search directory.