CSS_Kidd - 8:16 pm on Mar 4, 2009 (gmt 0)
I have done this. It is one of my favorite things to do... Just create a 10 x 10 (doesn't matter what size) and set the transparency to somewhere around 30 (between 30 and 20 is the best effect). Then export it as a png 32 transparent bg, no matte. Set it as a div's background image (repeat) and for IE 6 use a fix like Twin Helix so it will show up and wahlah! Semitransparent background... Looks great as a nice overlay to other background images.