Confirm boxes are a convenient way to give a web visitor a simple choice: to accept or to decline something. They are displayed using the JavaScript confirm function.

for example-

confirm("Text or question you want to use");

The code is as -

<script type="text/javascript">
function show(){
var c= confirm("This is the comfirm box");
if(c == true)
{
alert("You select ok");
}
if(c== false)
{
alert("You select cancel");
}
}
</script>