It's the worst thing that could happen to the traffic of your website. Being banned is search engines is a sort of penalization of a misleading act done by the webmaster in order to improve his ranking. So you'd better not cheat the spider !!
1- Avoid bad linking :
Never link to "bad ones" like gambling sites, adult sites and Warez. Specially when it has no relationship with your content. You have to administer your visitor's input like comments and censor any type of offending words or those who try to spam you with a lexical farm related to adult content in a way to create a group of keywords thus the spider will consider it as adult site and ban it!
2-Duplicate content :
Search engines can get too severe with copyright violation specially if somebody has claimed that your using his content. Even if you're trying to make a quot make sure that you put quotation marks (") and don't exaggerate.
3-Keyword spamming :
If you mess with the spider, it will bite you !! Some people try to blend keywords with the background of their design in a way that it will be only readable by spiders when they come to check keywords content. Another way of spamming called "sneaky redirects" it's to put a huge number of keyword in a page and redirect it to home page. Once you click on it in the result page you will be redirected to another page inviting you to buy something. Annoying isn't it ? That's why search engines get too severe about it.
If you want to improve your ranking you have to do it in the right way. Any misleading acts will put an end to your website growth !
