var specialURL = "imgs/special1.jpg";

if (document.images) {
     var special1 = new Image();
     special1.src = "imgs/special1.jpg";

     var special2 = new Image();
     special2.src = "imgs/special2.jpg";
	 
	 var special3 = new Image();
	 special3.src = "imgs/special3.jpg";

	 var special4 = new Image();
     special4.src = "imgs/special4.jpg";
	 
	 var special5 = new Image();
	 special5.src = "imgs/special5.jpg";	 
}

function changeSpecial() {
     if (document.images) {
        if (specialURL == "imgs/special1.jpg") specialURL = "imgs/special2.jpg";
		else if (specialURL == "imgs/special2.jpg") specialURL = "imgs/special3.jpg";
		else if (specialURL == "imgs/special3.jpg") specialURL = "imgs/special4.jpg";
		else if (specialURL == "imgs/special4.jpg") specialURL = "imgs/special5.jpg";
		
		
         document.mySpecial.src = specialURL;
	}
}