<script type="text/javascript">

setHour=1
setMin=1 // you can set using minutes only, 90 minutes = 1 hour 30 minutes
setSec=1

function initTimer2(){

nowHours=setHour
nowMins=setMin
nowSecs=setSec

if(setMin>=60){
nowHours=Math.floor(setMin/60) // using minutes
nowMins=(setMin%60) // using minutes
}

tickTheTock()
}

function tickTheTock(){

if(nowSecs==-1){
nowSecs=59
nowMins--
}

if(nowHours>0&&nowMins==-1){
nowHours--
nowMins=59
}

showHours=chkTick(nowHours)
showMins=chkTick(nowMins)
showSecs=chkTick(nowSecs)

document.getElementById("timerdiv").innerHTML=showHours+" : "+showMins+" : "+showSecs

if(nowHours==0&&nowMins==0&&nowSecs==0){
setTimeout("timesUp()",1000)
}
else{
nowSecs--
tickTimer=setTimeout("tickTheTock()",1000)
}

}

function chkTick(n){
if(n<10){
n="0"+n
}
return n
}

flashTimer=""

function timesUp(){
with(document.getElementById("timerdiv").style){
if(visibility=="visible"){
visibility="hidden"
color="F00000"
}
else{
visibility="visible"
}
}

flashTimer=setTimeout("timesUp()",1000)
}

function resetTimer2(){
clearTimeout(tickTimer)
clearTimeout(flashTimer)
document.getElementById("timerdiv").style.visibility="visible"
document.getElementById("timerdiv").style.color="008000"

initTimer2()
}

// add onload="initTimer2()" to the opening body tag

</script>

<div id="timerdiv" style="visibility:visible;color:008000"></div>