var url="";
var imgObjSupport = false;
if (document.images) {imgObjSupport = true;} else {imgObjSupport = false;} 
if (imgObjSupport) { 

bt1_off = new Image(); bt1_off.src = "http://www.thinkcomputers.org/images/bt_1.gif";
bt1_on = new Image(); bt1_on.src = "http://www.thinkcomputers.org/images/bt_1on.gif";

bt2_off = new Image(); bt2_off.src = "http://www.thinkcomputers.org/images/bt_2.gif";
bt2_on = new Image(); bt2_on.src = "http://www.thinkcomputers.org/images/bt_2on.gif";

bt3_off = new Image(); bt3_off.src = "http://www.thinkcomputers.org/images/bt_3.gif";
bt3_on = new Image(); bt3_on.src = "http://www.thinkcomputers.org/images/bt_3on.gif";

bt4_off = new Image(); bt4_off.src = "http://www.thinkcomputers.org/images/bt_4.gif";
bt4_on = new Image(); bt4_on.src = "http://www.thinkcomputers.org/images/bt_4on.gif";

bt5_off = new Image(); bt5_off.src = "http://www.thinkcomputers.org/images/bt_5.gif";
bt5_on = new Image(); bt5_on.src = "http://www.thinkcomputers.org/images/bt_5on.gif";

bt6_off = new Image(); bt6_off.src = "http://www.thinkcomputers.org/images/bt_6.gif";
bt6_on = new Image(); bt6_on.src = "http://www.thinkcomputers.org/images/bt_6on.gif";

bt7_off = new Image(); bt7_off.src = "http://www.thinkcomputers.org/images/bt_7.gif";
bt7_on = new Image(); bt7_on.src = "http://www.thinkcomputers.org/images/bt_7on.gif";

bt8_off = new Image(); bt8_off.src = "http://www.thinkcomputers.org/images/bt_8.gif";
bt8_on = new Image(); bt8_on.src = "http://www.thinkcomputers.org/images/bt_8on.gif";

bt9_off = new Image(); bt9_off.src = "http://www.thinkcomputers.org/images/bt_9.gif";
bt9_on = new Image(); bt9_on.src = "http://www.thinkcomputers.org/images/bt_9on.gif";

bt10_off = new Image(); bt10_off.src = "http://www.thinkcomputers.org/images/bt_10.gif";
bt10_on = new Image(); bt10_on.src = "http://www.thinkcomputers.org/images/bt_10on.gif";

}

function roll_on(imgName) {if (imgObjSupport) {imgOn = eval(imgName + "_on.src"); document [imgName].src = imgOn;}}
function roll_off(imgName) {if (imgObjSupport) {imgOff = eval(imgName + "_off.src"); document [imgName].src = imgOff;}}