Alright, I'm still pretty knew to the guitar and bass world, starting bass in february and guitar in December.

Anyways in a tab that I've been looking at (Red Hot Chilli Pepper's song By the Way) it has some notes with x's on them. I don't know what these means, expect that you are probably supposed to slap them...

So could someone enlighten me?

My Gear
Fender 60th Anniversary Standard Stratocaster
Washburn Lyon (LCT24)
Silvertone Revolver Bass
Ibanez IJV50 Acoustic
Fender CD160E-12
Guild Starfire IV
Some cruddy classical that my parents bought off ebay for like 40 bucks.
just mute the note

easiest way is to take the pressure off the string and fret and it will make a kind of precussive sound
most guys i've played with will mute all of the strings on the neck and slap them all with their right hand