On the Web tab, you can link any resource on the Web by entering its URL. On this tab, you can specify the same properties as described here, with the difference that the content of the General tab is displayed above the two other tabs.
Properties that can be specified for the link are described on this page.
Page url: http://devnet.kentico.com/docs/5_5r2/contexthelp/index.html?dialogs_link_web.htm