Parallax scrolling website interfaces have been popping up all over the place recently. I didn’t want to miss out on the fun, so I have put together a parallax scrolling demo built using jQuery and CSS.

How it works

The articles and background layers are given a fixed positioned with CSS, and assigned a z-index so that the foreground layers appear above the background layers. The four layers are: small clouds, large clouds, balloon/landscape images, articles.

/* foreground (ballons/landscape) */
#parallax-bg3 {
    z-index: 3;
    position: fixed;
    left: 50%; /* align left edge with center of viewport */
    top: 0;
    width: 940px;
    margin-left: -470px; /* move left by half element's width */
}

Within each layer individual content elements are absolutely positioned. This was the most fiddly part of the process, since the elements need to positioned in such a way that they align in a pleasing manner when the user scrolls to any of the four articles. In this case it was really just a process of trial and error.

#bg3-1 {
    position: absolute;
    top: -111px;
    left: 355px;
}
#bg3-2 {
    position: absolute;
    top: 812px;
    left: 321px;
}
/* etc... */

A few lines of jQuery control the parallax effect, triggered by a scroll event. I was surprised how easy this was to achieve, it is literally just a handful of lines of code.

$(window).bind('scroll',function(e){
    parallaxScroll();
});
 
function parallaxScroll(){
    var scrolled = $(window).scrollTop();
    $('#parallax-bg1').css('top',(0-(scrolled*.25))+'px');
    $('#parallax-bg2').css('top',(0-(scrolled*.5))+'px');
    $('#parallax-bg3').css('top',(0-(scrolled*.75))+'px');
}

Read more:http://f6design.com/journal/2011/08/06/build-a-parallax-scrolling-website-interface-with-jquery-and-css/