//preload images
var image1=new Image()
image1.src="images/mainpic_5.jpg"

var image2=new Image()
image2.src="images/mainpic_6.jpg"

var image3=new Image()
image3.src="images/mainpic_4.jpg"

var image4=new Image()
image4.src="images/mainpic_1.jpg"