When you host your own WordPress page and you get the error of a style sheet is missing (twentyfourteen – Stylesheet is missing) (especially when you upgraded from 3.7 to 3.8.x)
I had this issue with the Twenty fourteen theme. To fix this issue I had to do the following.
FTP to my webpage location. And I deleted the Theme which gave the error. After deleting it I add the theme again and it will install successfully. And you don’t have an error again.