Log analysis can tell you not only what sites your visitors originate from (whether your visitor arrives via a Search Engine or from a "regular" site), but also what keywords they enter (in the Search Engines) to find you. The keywords give you an idea of your prospects level of interest, as well as the kinds of benefits they seek.
Are you successfully drawing visitors through your site? A quick look at your log analysis report will tell you. Of the people arriving to your site, how many are pulled through your page joint to the next page (or stage)? Once you know how visitors act on your site, you will understand how to change your Web site in order to improve your Conversion Rate.
The only way to successfully market anything online is to track and measure your results. In fact, the ability to do this effectively is one of the most powerful benefits of doing business on the Internet.