function doPic_a(imgName,imgLoc) {
imgOn = ("" + imgName);
document.mainpic_a.src = imgOn;
//window.location=imgLoc;
}

function doPic_b(imgName,imgLoc) {
imgOn = ("" + imgName);
document.mainpic_b.src = imgOn;
//window.location=imgLoc;
}

function doPic_c(imgName,imgLoc) {
imgOn = ("" + imgName);
document.mainpic_c.src = imgOn;
//window.location=imgLoc;
}