onMouseover and onMouseout problems

[Shawn Windle]

<script language="javascript" type="text/javascript">

if(document.all)
{
/* IE 4+ */
document.write("<br><br><br><br><br>");
document.write("<center><h1>");
document.write("<span id='enter'
onMouseover='enter.style.color='red''
onMouseout='enter.style.color='yellow''>Enter</span>");
document.write("</h1></center>");
}

</script>

I want the word Enter to change color when I move the mouse over it. I
think the problem is in the line with the span tag. Can anyone help?
Thanks!