How much do you know about the people that frequent your website?  If the answer is "Not much", then perhaps it's time to conduct a few online surveys and get an idea of the kind of person that enjoys your content. Understanding your visitors can help you to focus your web development efforts, and is also useful for attracting advertisers. The more information you can provide about your demographics, the more targeted the advertisements on your site can be.  Better targeting translates into more conversions, and hopefully more money from those ads.