I do not have any sound. I tried going to volume control in system preferences but that didn't help. I cannot hear anything when I am on youtube. What do I do?
Do you have sound otherwise? Is it purely an issue when you are trying to watch a YouTube video? Have you checked the YouTube window volume control slider?
If sound works everywhere but youtube, it's probably browser/plugin-related. Simply restart your browser and try again - or download a different browser to try it there. Youtube is using the Flash-plugin.