x note?!

when i want to learn a new song on my guitar and read a tab, then sometimes i see this : ''x'' i thought they called it a ''dead note''
okay, here comes the stupid question, what does it mean?! how do i have to play it? :confused:

It depends on how the tabber means it. Either a palm mute or a string that you skip. If you dont know how to palm mute: Just take your palm and rest it across the bridge and slightly on the strings so you hear the fret being muted not just a dud. The more you put your hand twards the nut, the less notes you'll hear, the closer you are to not have the strings muted, the more you'll hear. If that don't help go here. What song you learning?

I'm learing ''Polly'' - Nirvana

Looking at the tabs its palm mutes. GL.