URLs follow a standard pattern that consist of several elements, the most important of which is the protocol used to access the resource (e.g. http:// for HTTP-based requests, ftp:// for FTP, etc.)
In this case you're trying to download a link using the 'wsytd' protocol. This is not a standard protocol at all, but appears to be something related to WonderShare, a third-party app for downloading content from YouTube.
As such, the problem is not with your machine, or Safari at all, it's with some kind of Wondershare app.
Either Wondershare isn't installed on your machine (so the OS doesn't know to pass wsytd:// URLs to it), or the app is broken in some way. A quick search on the net finds this discussion which indicates that you're not alone and alludes to the possibility that YouTube have moved to block this app from downloading content (presumably on some copyright basis). If that's the case then your recourse is to go to the software vendor to look for updates that might work. Either way, it's not your Mac, per se., that's at fault.