From this tab, you can link any resource on the web by entering its URL. 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.
Detailed information about the WYSIWYG editor can be found in the WYSIWYG editor chapter in the Content management section of the Developer's Guide.
Page url: http://devnet.kentico.com/docs/6_0/contexthelp/index.html?dialogs_link_web.htm