agent = navigator.userAgent;
  rollovercheck = 0;
  if (agent.substring(0,7) == "Mozilla")
  {
    if (parseInt(agent.substring(8,9)) >= 3) { rollovercheck=1; }
    if (agent.indexOf("MSIE 3") != -1) { rollovercheck=0; }
  }

if (rollovercheck) {  // If browser is acceptable, preload images
                                          
jvkco1 = new Image();
jvkco1.src ="images/nav/stock.gif";
jvkco1a = new Image();
jvkco1a.src ="images/nav/stockover.gif";
jvkco2 = new Image();
jvkco2.src ="images/nav/about.gif";
jvkco2a = new Image();
jvkco2a.src ="images/nav/aboutover.gif";
jvkco3 = new Image();
jvkco3.src ="images/nav/services.gif";
jvkco3a = new Image();
jvkco3a.src ="images/nav/servicesover.gif";
jvkco4 = new Image();
jvkco4.src ="images/nav/portfolio.gif";
jvkco4a = new Image();
jvkco4a.src ="images/nav/portfolioover.gif";
jvkco5 = new Image();
jvkco5.src ="images/nav/contact.gif";
jvkco5a = new Image();
jvkco5a.src ="images/nav/contactover.gif";
jvkco6 = new Image();
jvkco6.src ="images/nav/prices.gif";
jvkco6a = new Image();
jvkco6a.src ="images/nav/pricesover.gif";

}

function changeImage(imgDocID,imgObjName) {

   if (rollovercheck) {  // If browser is cool, swap images
   {document.images[imgDocID].src = eval(imgObjName + ".src");}
                                }
}