function changesrc(){

var main=document.getElementById("productMainImage");
var mp=main.getElementsByTagName("img")[0];
var ma=main.getElementsByTagName("a")[0];
var imgm=mp.src;

var sp=document.getElementById("productAdditionalImages");
var spic=sp.getElementsByTagName("img");

var sp2=document.getElementById("pai");
var spic2=sp2.getElementsByTagName("img");

for( var i=0 ;i<spic.length;i++)
{
	spic[i].num=i;
	spic[i].onmouseover=function()
	{
	
		for(var j=0;j<spic.length;j++){
			if(j==this.num){			
				ma.href=sp.getElementsByTagName("img")[j].src;
				mp.src=sp2.getElementsByTagName("img")[j].src;
				
				//spic[j].src=imgm;
				sp2.getElementsByTagName("img")[j].src=imgm
				
			}
			
		}
	}
}

}