var backgroundSrcs = new Array("images/displaypic02.jpg",
"images/displaypic03.jpg",
"images/displaypic04.jpg",
"images/displaypic05.jpg",
"images/displaypic06.jpg",
"images/displaypic07.jpg",
"images/displaypic08.jpg",
"images/displaypic09.jpg",
"images/displaypic10.jpg",
"images/displaypic11.jpg",
"images/displaypic16.jpg",
"images/displaypic17.jpg",
"images/displaypic18.jpg",
"images/displaypic19.jpg",
"images/displaypic20.jpg",
"images/displaypic14.jpg") 
function pickimage() 
{ 
var bgimage=backgroundSrcs[(Math.floor(Math.random()*(backgroundSrcs.length-1)))] 
document.getElementById("topnav").style.background = "white url('" + bgimage + "') no-repeat right top"; 
}