// randomise main background

var bgnds=new Array('images/bg1.jpg', 'images/bg2.jpg', 'images/bg3.jpg', 'images/bg4.jpg', 'images/bg5.jpg', 'images/bg6.jpg', 'images/bg7.jpg');

function randbg()
{
      var mainbg=document.getElementById('mainimage');
      var bgimgurl=bgnds[Math.floor(Math.random()*7)];
      var bgimg="url('"+bgimgurl+"')";
      mainbg.style.backgroundImage=bgimg;

if (bgimgurl=='images/bg4.jpg')
	{
	document.getElementById('mainheading').innerHTML="Are you looking for cytometry controls<br /> that are stable for up to 90 days?";
	}

if (bgimgurl=='images/bg7.jpg')
	{
	document.getElementById('mainheading').innerHTML="Are you looking to stabilise<br /> antigens for up to 10 days?";
	}


}