If you happened to applied a wrong skin, and you can not go in to the site anymore. There is a simple method can reset your skin to default if your login is not timed out yet.

Simply add this

/Host/Skins/tabid/35/portalid/0/Default.aspx?SkinSrc=[G]%2fskins%2fdnn-blue%2fhorizontal+menu+-+full+width

to your domain. And you can click the reset to default.