Every small business owner knows the importance of a high search engine ranking. SEO experts and internet marketing professionals have built their careers around figuring out how to help their clients achieve top rankings, and small business owners draw on that expertise every day. But whether you've done your own search engine optimization or had a professional do it on your behalf, things sometimes go wrong. If search engines believe that you're spamming or using any other off-limits methods of optimization, you will be banned, often without even realizing it. Here are 5 sign that you've been penalized by Google.

1. You Have a PageRank of 0. PageRank is Google's method of ranking the popularity and relevance of websites. If Google had previously ranked you, but you noticed that your current PageRank is 0, you can almost guarantee that Google has penalized you. Before you panic, remember that new websites always begin with a PageRank of 0, so you should only worry if you once had a PageRank above 0 and currently have a PageRank of 0.

2. Your Website Isn't Indexed. If your pages no longer show up in Google's index, then chances are you've been penalized. Think of a keyword for which your site has ranked in the past and plug it into the search field on Google. Where is your site? If you've dropped from the first page of results to the second, don't panic. Just make a note of it and improve your search engine optimization. But if your site doesn't show up at all for that particular keyword, then there's a problem. Remember also to ensure that your homepage isn't the only page appearing in the search results. A minor penalty will sometimes result in only your homepage appearing rather than your homepage plus other subpages.

3. Use Your Tools. Google's Webmaster Tools is a great way to see how often Google looks at your website. If you use Webmaster Tools and notice a red sign next to your domain name, Google has penalized you. Webmaster Tools will also tell you how many inbound links you have from other sites. Don't forget to check on all of your pages. If Google isn't seeing some of them, be sure to resubmit them.

4. Use Analytics. Search the web for free analytics tools to tell you whether or not Google has banned you.

5. Google Search Your Domain. Using Google, type in “site:http://www.yourdomain.com.” The results you see will tell you how many pages within your website Google has indexed. When you're typing in this request, use a lowercase “s” since using an uppercase “S” will cause the request to work improperly.

Search engine optimization can be a tricky process, especially if you're not familiar with its evolution and all the reasons Google has for banning certain practices. If you're unsure of your ability to optimize your site properly, consult an SEO expert or internet marketing professional. And if you discover that you have been banned, seek the help of an SEO professional to help you determine what mistakes you might have made in your optimization process. When you're up to your eyeballs in your own webpage, it's often hard to see what you might have done wrong. Let someone else look for possible errors and problems. You'll be glad you did when your site is once again receiving top rankings from Google!