If you have your own web page or site then you are probably interested in how many people are visiting your page. In order to track this you may have placed a counter on your page or you may have access to the web logs that track this without having to place a counter.
The problem with such statistics as you might obtain is in determining just exactly what it is that you are measuring. Are you counting hits, views, or visitors?
More useful is to count page views. Instead of counting each file that is being downloaded to display your page we want to count only one for each time that the entire page is requested. Many of the counters that I have seen place an image (often a transparent image only one pixel in size) on each page that is to be counted. In each instance the image file is given a different name and the number of requests to download these individual files equates to the number of page views. These images are often attached to the very end of the page source so that only those visitors who wait for the entire page to download will be counted. Of course if the same person downloads the same page again then they will be counted again. Another problem with counting downloads is that in many instances at least some of the files required for the page will already be in your visitor's cache and so may not be downloaded again when they revisit. Unfortunately you can't rely on this always being the case and so you cannot use this count as a count of visitors. To get an accurate page view count requires that the file being used for the counter be always retrieved from the source location and not be available from your visitor's cache or any mirror or proxy site.
Counting unique visitors is the most meaningful statistic but is the hardest to obtain given the anonymity of the web. About the only way to accurately determine if the page is being viewed multiple times by the same person is to place a cookie on their computer at the time they first visit. If they have cookies disabled then you can't do this. Even where you can, the cookie will not stay there forever, an appropriate expiry period will be needed after which a new visit to the page by the same person will be counted as an additional visitor by the counter. The only other possible way of attempting to track unique visitors is by storing the IP addresses and assuming that two visits from the same IP address are being made by the same person which will not always be correct.
This article written by Stephen Chapman, Felgall Pty Ltd.