Mobile safari position:fixed z-index glitch when scrolling

z-index is not reliable with position:fixed, as shown in this fiddle: http://jsfiddle.net/mZMkE/2/ use translateZ transformation instead.

transform:translateZ(1px);

on your page elements.

EDIT: In your code, Add this css:

.bla, .projects, .contact  {
      -webkit-transform:translateZ(1px);
      -moz-transform:translateZ(1px);
      -o-transform:translateZ(1px);
      transform:translateZ(1px);
}

and then remove z-index refs from those elements and .intro.

Update 1: I added transform:translateZ(x) in addition to the z-index and it did not fix the problem.

Update 2: I added -webkit- prefix and this DOES fix the z-index problem on mobile Safari, but also causes the position:fixed to work incorrectly in desktop Chrome. "

Then try to wrap -webkit-transform:translateZ(x) in a mobile specific media query.
For example:

@media only screen and (min-device-width : ... ) and (max-device-width : ... ) {
    .whatever {
        -webkit-transform: translateZ(x)
    }
}

So in this case it won't do anything on desktop Chrome

I tried the solution accepted as an answer in a specific case when I needed to set different position in the stack of different layers, but that alone didn't work both in desktop browsers (firefox and chrome) and Safari iOS

I came out with this hack which uses both translateZ and z-index for each div, which is working in those platforms. The order of translateZ and z-index is important. For setting each layers position is

-webkit-transform:translateZ(1px);
-moz-transform:translateZ(1px);
-o-transform:translateZ(1px);
transform:translateZ(1px);
position: relative; 
z-index: 1; 

I used the same value for the z-index and translateZ just for consistency, it is not necessary. See working example http://jsbin.com/peyehufo/5