The trick to getting screen grabs from that site without the shadow thingys is, once you have the image positioned where you want it, place your cursor over your browsers scrollbar at about the halfway point and just wait. Those shadow bars should disappear. Then just make sure you don't move your cursor over your browser again until you've done your grab, doing so will cause it to reappear.

If only the top or bottom bar disappears, just move your cursor up or down a bit and try again until you find the "sweet spot". Works well enough for the one page spreads ;-)