Thread:Project:Support desk/Skin.php suddenly failing to open correctly/reply

Well, hopefully the error message you get is verbose enough to figure out the problem: PHP is expecting to have /home/content/54/10246254/html/wiki/skins as a directory, but either it doesn't exist, it isn't a directory or the process running PHP doesn't have enough permissions to read it.

Check whether that path exists on the server and if the web server process is able to read it (check its permissions).

If you have accidentally lost that directory, you can recover it from the MediaWiki installation package (be sure to use the same version you were running). If you don't remember deleting it, it may be a filesystem corruption going on the server, or your server was compromised and somebody (or a malicious script) is deleting its contents.