Speakers work but not on internet (youtube)

I'm Prob just an idiot but all of a sudden when i logged on to youtube.com i noticed that that sound of my speakers did not work when i go to my audio files on my desktop they work fine I use mozilla Firefox I just dont get why Firefox wont let it work I have had my Gateway GT5056 for a year now and this has never happened Any help?



Thanks

try on ie. or clear the cache by i think going to tools, clear privet data i think.