If you go to your own site often, chances are that you will want to exclude your own visits from the stats so as not to inflate your results artificially. That is the purpose of the 'Exclude my own visits' setting.
If you click Yes, whenever you load your own site, Web-Stat will recognize your browser and will disregard the visit. If anybody else comes to your site, the visit will be counted normally.
If you click No all visits will be counted, including yours.
Important Note : when you exclude yourself from the count, you actually tell Web-Stat to exclude your browser. If you use several browsers (on the same computer or on different computers), you need to connect to Web-Stat with each one of them, go to the Control Panel and set the exclusion.