URL's / web address need to be in the right format. Because there are so many ways of typing URL's, this option ensures your URL is correct. When it is enabled it looks at what you have entered (when you close the dialog box or apply your changes) and corrects the URL. For example, if you enter "www.xara.com" it will correct it to "http://www.xara.com/". The URL is corrected when you click the Add or Change button.