The volume for my safari is disabled.

I got my macbook from the apple store the other day to fix a cracked screen. When I got it back, I tried watching videos on safari and it kept muting. I went to different websites and got the same result. Youtube. Hulu. You name it. I then went to my itunes and played the movie Inception and the volume worked fine. I went onto google chrome and the volume worked fine. I went onto Final Cut and the volume worked fine. But the volume on Safari is disabled. I went looking for help topics on volume control, but miraculously, there were none. Absolutely zero. Can anyone help me, or is Apple getting one over on me again like how they sell fingerprints on Iphone 5s unlock feature to the NSA?