function checkUnique(arr, value) {
			var size = arr.length;			
			for (var i = 0; i < size; i++) {
				if (value == arr[i]) return false;
			}
			arr.push(value);
			return true;
		}
		
		//the following code will execute after the corresponding pictures placeholders have been loaded 
		var picsNumber = 9;
		var arr = new Array();
		
		for(var j = 1; j <= 4; ) { 
			var random = Math.random();
			var picnum = picsNumber * random + 0.5;
			picnum = Math.round(picnum);
			if (checkUnique(arr, picnum) == false) continue;
			var image = document.getElementById("demoimg" + j);
			if (image) image.src = "files/verticaldemo/dfpic" + picnum + ".gif";
			j++;			
		}