Added bit on Google Analytics Tools:
Every webmaster likes to monitor their site closely. For instance, the most basic need is to know just how many people are visiting your site on a daily basis. It is also useful to know where they are coming from. Some of you visitors (also called traffic) will be coming from search engines, others will be coming through links to your site that have been placed on other websites. In order to increase the effectiveness of your SEO campaign, then you need to have a full and detailed breakdown of these sorts of statistics.
This is where Google's free Analytics Tools comes in handy.
Like their Webmaster Tools, this is free to use and is activated by placing code into your website.
For Google Analytic Tools you will place the code in your footer which Google will provide to you
As it happens, you can place the code in your header, but the reason why it should be placed in your footer is because it will decrease the load time of your page.
Google's Analytic Tools are now considered so advanced that it is used by professionals in the SEO and webdesign industry over other paid options.
It offers many advanced features. As an example, it will tell you the screen resolution of your visitors such as 800 x 600 or 1024 x 768 or even just what type of browser a visitor is using.
Analytics Tools will also give you information such as what keywords visitors are using in search engines when they came across your website.
For an introduction to Google's Analytics Tools read their guide
here.
The best way of understanding what Google Analytics offers is by joining yourself and exploring its many complex features.
If you do have any questions regarding this tool, then post it up in this forum and others will be able to assist.