continuo a fare tentativi, ma ancora non arrivo al risultato, posto il codice, forse qualcuno e' cosi gentile da modificarlo:

<HTML>
<HEAD>


<TITLE>Javascript: countdown </TITLE>


</HEAD>

<BODY bgcolor="white">


<script language="JavaScript">

<!-- Hide the script from old browsers --

var up,down;

var day1,hour1,min1,sec1;

var cday1,hour1,cmin1,csec1,cday2,hour2,cmin2,csec2;

function day(data) {

for(var i=0;i<data.length;i++) if(data.substring(i,i+1)==":") break;

return(data.substring(0,i)); }

function Seconds(data) {

for(var i=0;i<data.length;i++) if(data.substring(i,i+1)==":") break;

return(data.substring(i+1,data.length)); }

function Display(min,sec) {

var disp;

if(day<=9) disp=" 0";

else disp=" ";

disp+=min+":";

if(hour<=9) disp+="0"+sec;

else disp+=sec;

return(disp); }

if(min<=9) disp=" 0";

else disp=" ";

disp+=min+":";

if(sec<=9) disp+="0"+sec;

else disp+=sec;

return(disp); }

function Up() {
cday1=0;

chour1=0;

cmin1=0;

csec1=0;

day1=0+days(document.sw.beg1.value);

hour1=0+hours(document.sw.beg1.value);

min1=0+Minutes(document.sw.beg1.value);

sec1=0+Seconds(document.sw.beg1.value);

UpRepeat(); }

function UpRepeat() {
cday1++;

if(cday==24) { cday1=0; chour++; }

chour1++;

if(cmin1==60) { chour1=0; cmin1++; }
csec1++;

if(csec1==60) { csec1=0; cmin1++; }

document.sw.disp1.value=Display(cmin1,csec1);

if((cmin1==min1)&&(csec1==sec1)) alert("Timer-CountUp Stopped");

else up=setTimeout("UpRepeat()",1000); }

function Down() {

cmin2=1*Minutes(document.sw.beg2.value);

csec2=0+Seconds(document.sw.beg2.value);

DownRepeat(); }

function DownRepeat() {

csec2--;

if(csec2==-1) { csec2=59; cmin2--; }

document.sw.disp2.value=Display(cmin2,csec2);

if((cmin2==0)&&(csec2==0)) location.href=('.............htm')

else down=setTimeout("DownRepeat()",1000); }



// --End Hiding Here -->

</SCRIPT>

<TABLE BORDER=1>
<TD WIDTH=340 ALIGN=LEFT>

<form name="sw">


<table border="3" width="75%">

<tr><th colspan="2">Countdown</th></tr>

<tr align="center"><td>Start at
<input type="text" name="beg2" size="7"

value="00:10"></td>

<td><input type="button" value="Start" onclick="Down()"></td></tr>

<tr align="center"><td colspan="2"><input type="text" name="disp2"

size="9"></td></tr>

</table>




</form>


</body>

<script language="JavaScript">
<!--

window.open = SymRealWinOpen;

//-->
</script>


Ringrazio anticipatamente.