To write messages to the screen without using "document.write()" ?

Changing the contents of an element is a much better solution. When the method showStatus is invoked it will change the content of the span.

...

function showStatus(message) {

var element = document.getElementById("mystatus");

element.textContent = message; //for Firefox

element.innerHTML = message; //for IE (why can't we all just get along?)

return true;

}

...

<span id="mystatus">Test. </span>

...