Google has added the ability for webmaster to instruct Google to ignore URL parameters in Webmaster Tools. URL parameters are name/value pairs appended to end of URLs (example: http://www.example.com?sessionid=1232132). The problem with URL parameters is that each URL created by a variation of parameter may or may not change the contents of a web page, so search engines treat each version as a separate web page. When they are actually the same it can have as serious negative impact on the indexing and ranking of the pages in search engines. In general it is better not use URL parameters in these situations, but the new feature should help to better handle situation where they do exist. In help documentation for the new feature, Google states that up to 15 parameters can be set to be ignored and that they will treat the “requests as suggestions rather than directives.” Parameter handling can be found in the Settings section of the Webmaster Tools. Yahoo has provided the ability to set parameters to ignore, as well as well allowing a default value to be set for parameters, for some time.