Your site may have a page that can be reached through more than one URL variation – with and without WT.mc_id for example. This can cause search engine spiders to record more than one URL for that page, and that’s a bad thing. You can prevent the marker parameters (such as WT.mc_id) from being recorded by spiders, by using canonical link-tags.

If you keep up with web analytics news, you may or may not know about the recent fuss over the behavior of a free, widely-used virus-protection program from the company AVG.