The classic use of these two event handlers is for JavaScript rollover images. In the the following example , when you move move your mouse over the link the "onMouseOver" event of the link is fired , and on the text box it is shown. Similerly , when the mouse moves away from the link, "onMouseOut" event of the link is fired .
The Code
<form name ="f1">
<center>
<input type="text" name="status" value="mouse on the Link">
<br>
<a href="" onmouseover=" document.f1.status.value='mouse on the Link'"onmouseout="document.f1.status.value='mouse Not on the Link'">Move the Mouse Over Me!</a>
</center>
</form>
onKeyUp
This event fires when user moves his finger out of a key. In the following example there are two textboxes , user types on the first textbox and the value is autometically copied to the other textbox.
<form action="" name ="f3" method="get">
<p>
<input name="t1" type="text" value="Type Something" onKeyUp="document.f3.t2.value=document.f3.t1.value">
</p>
<p> <input name="t2" type="text" id="t2">
</p>
</form>