Last week, Had an announcement from Yahoo, Msn and Google that all are going to support a new link element to resolve duplicate content issues on canonical urls. This Link element would be the biggest change and best practice of SEO.
All SEO's, web masters and web developers should make a note of it. Most of sites which have these issues were not able get good rankings in search engines. Especially with session ids this problem will occur mostly to the E-commerece sites and travel websites. They all need to implement it rightway on their sites to get better rankings.
Canonical urls :
Search Engines (Google, Yahoo & MSN) would think of that those are three different urls, having different content. Usually those all urls have the same content. Most of the webmasters are having this major problem. At last now Google, Yahoo & MSN fixed it by introducing a new link element.
Fixing Canonical urls :
Insert the link tag as shown below in between header tags.
Have a look on the following major links which were discussing about fixing the canonical issues :
Matt cutts explanation with Presentation :