Google (web) Analytics is now free for websites that have less than 5-million page views. If you don’t have an analytics tool already, you should check it out.
Research shows that the number one priority for B2B websites is lead generation. In the task of converting inquiries to leads and ultimately in determining the return on investment, your web site log files are an important tool for measuring to what extent search engine optimization is working.
By pinpointing where traffic originates and the accompanying click-stream, you have the means of tracking the path visitors are taking to your site. Log files can be tied into the database to view how often a visitor clicked on and the attendant clickstream (pages visited and in what order).
In the complex sale, the length of the buying cycle makes the connection between on-the-web activity and the off-line decision to purchase much more difficult to trace. So the challenge is connecting website log file data (analytics), with marketing data (inquiries) and then connecting them with the sales process.
I wrote a piece a while back on Tracking ROI From Web Generated Leads