Search engines hate query strings. For example, say you have a website that sells widgets. You have four types of widgets: red, green, blue and black. You have a page titled Inventory.aspx that accepts a query string to show each of the widgets, like this: www.MyWidgetSite.com/Widget... To make this more SEO friendly, you could have a URL like this: www.MyWidgetSite.com/Widget... That allows a search engine to index the site easier, and to more easily identify relevant content for search ......