Google Hell !, What a term, some are very familiar with this term, and this may be your first introduction to such for others. 

    What is Google hell ? Google getting larger ever day realized some pages it was indexing were already indexed with a different URL thus creating what is know as duplicate content. Plus other known and unknown problem may through your site into Google Hell known by google as the supplemental index. This index is rarely used unless Google cannot find any other relevant content to match the search criteria.. Basically your pages will sit there with no visitor or hits from the search engines because of bad programming on the part of your site administrator or Website Programmer.

The main cause I see for sites getting thrown into the supplemental index is due to duplicate content. How does this come about?. If you run a Website system that produces dynamic content (pages on the fly) you might want to check and make sure your pages are being indexed properly. You could have over half of your site listed in the Supplemental Index. Thus killing your returns on your investment of time and money.

The problem explained: Duplicate content is a by product of cheap software, like OsCommerce,CreLoaded,ZenCart and other software that creates your pages on the fly from a database or other content available that has SEO applied. On their own their pretty much ok and will get you some decent listings. Top 100 or so. If your do your homework and cover the basics well you can get an out-of-box install to reach Top ten status. At this point a little knowledge can be dangerous, as you realize that your competition has URL's like " http://example.com/goodnews.html" and you have http://example.com/product_info.php?products_id=342" , at that point of knowledge you realize that can't be good, even all I've read say's thats not a good thing. In search of a fix you get into what is known as SEO "Search Engine Optimization".