You Can Make URLs as Extension Less by setting the Friendly URL extensions to ;;.aspx, this setting will set extension less as the main url, but also render pages with the .aspx extension. Alternatively If you are simply trying to prevent the .aspx extension from being added on postback, you can add the key "CMSUseExtensionOnPostback" to your web.config file and set this value to false. By Ray Business Technologies (http://raybiztech.com/solutions/epcm/kentico-epcm-solutions)
