I think it would be helpful for our users to know what things they should avoid doing so they do not get black listed from any of the search engines. Any recommendations?

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www.smallbusinessforum.com

Spamming has to be the number one reason sites get black listed

Using programs that submit an URL to many search engines.
Creating web sites and web pages with duplicated contents.
Using tricks to "fool" the search engines - spamming with keywords, using text with the same color as the page background, etc.

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MBM | Review your host | Know Vista?

I heard of people getting black listed using SEO optimizer programs and crawling the search engines too much.

Search engines are looking for "natural" activity meaning things happening with your site that would take around the same time and have the same results if you did it the normal way. So doing anything that causes excessive results may black list you are reduce your page results.

How do you know when you are black listed?

There maybe, but I am not aware of a site where you can go to to see if you are black list you will just see a drop traffic to your site. I am told at least with google you can appeal the decision but it takes time. The best thing you can do is avoid doing the wrong things in the first place.