Grainy images in JQM header...Why?

Grainy images in JQM header...Why?

Can anyone tell me if jquery automatically scales my header image and makes it grainy?  All images are very crisp except this logo image that appear in the header using the class="ui-btn-right".  Should it be sized to a specific height to avoid re-sizing and grainy appearance?  Any suggestions would be appreciated.

<div id="header" data-role="header">
        <h1>Cummins West</h1>
        <img class="ui-btn-right" src="/mobile/images/m-cwi-logo.png" alt="Cummins West Inc." />
        </div>

Here is the link to the site: http://www.cumminswestinc.com/mobile/

This logo at the top right of all pages and is grainy in all locations.

Thanks.