Then do just that :)
Nest each div inside a "container div" with a z-index of say 100 and opacity of 0.3;
//make all overlays opacity=0.3
$.each($("div.overlay"),function(i,val){
$(this).css( opacity , 0.3);
});
<div id="section1" class="overlay" style="z-index:100;" >
<div id="YOURSECTION HERE"></div>
</div>
<div id="section2" class="overlay" style="z-index:100;" >
<div id="YOURSECTION HERE"></div>
</div>
<div id="section3" class="overlay" style="z-index:100;" >
<div id="YOURSECTION HERE"></div>
</div>
Then i would make a function that disables or enables certain section on the click event of the continue button - something like:
function ChangeOverlay(oldOverlayID,newOverlayID)
{
//disable old section
$("#" + oldOverlayID).css( z-index ) = 100;
$("#" + oldOverlayID).css( opacity ) = 0.3;
//enable new section
$("#" + newOverlayID).css( z-index ) = -1;
$("#" + newOverlayID).css( opacity ) = 1;
}
Something like that :)