Web statistics are a very important part of web site development and marketing. Every day you collect statistics for, you are gathering valuable information to use in your marketing strategy. There is nothing better than looking at a document full of graphs showing increases in users or traffic; however, reading them and understanding how to use them effectively are two very different things.
When collecting stats, you could install multiple different statistics systems for the same set of data but more often than not no two systems will absolutely agree and this is where the biggest problem lies.