// function that displays mouseover image
if (document.images) {
up01 = new Image(583, 38); up01.src = 'http://www.avma.org/images/links_topnav.gif';
over01 = new Image(583, 38); over01.src = 'http://www.avma.org/images/links_topnav_1hi.gif';
up02 = new Image(583, 38); up02.src = 'http://www.avma.org/images/links_topnav.gif';
over02 = new Image(583, 38); over02.src = 'http://www.avma.org/images/links_topnav_2hi.gif';
up03 = new Image(583, 38); up03.src = 'http://www.avma.org/images/links_topnav.gif';
over03 = new Image(583, 38); over03.src = 'http://www.avma.org/images/links_topnav_3hi.gif';
up04 = new Image(583, 38); up04.src = 'http://www.avma.org/images/links_topnav.gif';
over04 = new Image(583, 38); over04.src = 'http://www.avma.org/images/links_topnav_4hi.gif';
up05 = new Image(583, 38); up05.src = 'http://www.avma.org/images/links_topnav.gif';
over05 = new Image(583, 38); over05.src = 'http://www.avma.org/images/links_topnav_5hi.gif';
up06 = new Image(583, 38); up06.src = 'http://www.avma.org/images/links_topnav.gif';
over06 = new Image(583, 38); over06.src = 'http://www.avma.org/images/links_topnav_6hi.gif';
up07 = new Image(583, 38); up07.src = 'http://www.avma.org/images/links_topnav.gif';
over07 = new Image(583, 38); over07.src = 'http://www.avma.org/images/links_topnav_7hi.gif';
up08 = new Image(583, 38); up08.src = 'http://www.avma.org/images/links_topnav.gif';
over08 = new Image(583, 38); over08.src = 'http://www.avma.org/images/links_topnav_8hi.gif';

}

function di(id,name){
  if (document.images) {document.topnav.src=eval(name+".src"); }
}
<!--
///capture client resolution
var ResImg = "http://avma.org/rss/images/rss.gif?res="+ window.screen.width + "x" + window.screen.height;

//-->