Knowing how long it takes for your pages to load and what browser and platform your customers are using can be very helpfull...

<SCRIPT LANGUAGE="JavaScript">

<!-- Begin
var startTime = new Date();
startTime = startTime.getTime();

function doneLoading() {
var stopTime = new Date();
stopTime = stopTime.getTime();
document.form1.LOADING_TIME.value = ((stopTime - startTime) / 1000)
+ " seconds";
document.form1.PAGE.value = document.title;
document.form1.SUBMITTER.click();
}

function checkForDuplicate() {
if (document.form1) {
document.form1.REFERRER.value = document.referrer;
document.form1.PLATFORM.value = navigator.appName
+ " " + navigator.appVersion;
return true;
}
else {
return false;
   }
}


// End -->
</script>

<BODY onLoad="doneLoading()" bgcolor="#00FF00">
<SCRIPT LANGUAGE="JavaScript">
  <!--
  var now = new Date();
  // -->
  </SCRIPT>
<FORM name="form1" METHOD=post action=" " onSubmit="return checkForDuplicate()">
<input type="hidden" name="PAGE" value="none">
<input type="hidden" name="LOADING_TIME" value="none">
<input type="hidden" name="REFERRER" value="none">
<input type="hidden" name="PLATFORM" value="none">
<input type="submit" name="SUBMITTER" value="Ok">
</form>