Swap images using html and css

Hello mates,

May I ask for some help here?

I’m trying to swap two .png images following a tut from webdesignerwall.com but I can’t seem to make it work. Actually is this the best way to swap images? css?
Currenlty the codes I have for one image are:
*HTML: **
<div id=“contact”>
<img src=“images/contact.png” title=“Contact | Work Inquiries” width=“291” height=“12” border=“0” alt=“Contact | Work Inquiries”/>
</div>
CSS:
#contact { padding:10px 0 0 0; width: 850px; border-top:1px solid #171717;/
border-bottom:1px solid #0f0f0e;
/}

I appreciate any help in advance,

Thank you very much,