var randomTWD = 0;
var DoIt = 0;
images = new Array;
images[1] = new Image();
images[1].src = "images/main-img.gif";
images[2] = new Image();
images[2].src = "images/main-img1.gif";
images[3] = new Image();
images[3].src = "images/main-img2.gif";
images[4] = new Image();
images[4].src = "images/main-img3.gif";
images[5] = new Image();
images[5].src = "images/main-img4.gif";
images[6] = new Image();
images[6].src = "images/main-img5.gif";

function TWDpics()
{
var imgnum = images.length - 1;
do 
{
var randnum = Math.random();
randomTWD = Math.round((imgnum - 1) * randnum) + 1;
}
while (randomTWD == DoIt);
DoIt = randomTWD;
document.PictureBox.src = images[DoIt].src;
}