[Old Pedant]

Look at this line in the code:

function putspan(backcolor, forecolor) {
 document.write("<span id='cntdwn' style='background-color:" + backcolor + 
                "; color:" + forecolor + "'></span>");
}

What *I* would do is change that to simply:

function putspan( ) {
    document.write( '<span id="cntdwn"></span>' );
}

And then use CSS <style> to set the color, background color, font, font-size, etc., etc., on that span:

<style type="text/css">
span#cntdwn { ... your specification here ... }
</style>