..
<title>original title</title>
..
<script type="text/javascript">
function changeTitle(title) { document.title = title; }
</script>
..
<input type='button' onclick='changeTitle("new title")' value='Change Title'/> 
..

<script type="text/javascript">
function changeText(txt){
	document.getElementById('the_text').innerHTML = txt;
}
</script>
<p>Hello <b id='name'>World</b>. </p>
<input type='button' onclick='changeText("Oliver")' value='Change Text'/>