3 standard (IEEE 802) formats:

* 0a:1b:3c:4d:5e: 6f
* 0a-1b-3c-4d-5e-6f
* 0a1b.3c4d.5e6f



Code:
<script type="text/javascript">

	teststr="0a:1b:3c:4d:5e:6f";
	
	regex=/^([0-9a-f]{2}([:-]|$)){6}$|([0-9a-f]{4}([.]|$)){3}$/i;
	
	if (regex.test(teststr)){
		document.write("Valid mac address");
...