Skype Click to Call plugin is no longer available for Safari on Mac OS X Mavericks. This is because of plugin just not compatible with Safari browser. Skype team is working to make it available again, meanwhile if you’ve installed this plugin Skype team recommending to disable it on Mavericks, here is how to do that.
Disabling Skype Click to Call for Safari in Mac OS X Mavericks
1. Open Preferences in Safari.
2. Click on "Extensions "and uncheck "unable Skype click to call" box.