Never redirect to another domain
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
Invisible images are images that are 1×1 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
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
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
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.
Don’t Use Doorway Pages
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.
Don’t Cloak Websites
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.