Set the DIV's z-index to one larger than the other DIVs. You'll also need to make sure the DIV has a position
other than static
set on it, too.
CSS:
#someDiv {
z-index:9;
}
Read more here: http://coding.smashingmagazine.com/2009/09/15/the-z-index-css-property-a-comprehensive-look/