My menu displays a .png file with smooth edges in most browsers, but in Internet Explorer it appears with rough edges. Can someone help me understand why IE treats .png files differently compared to other browsers?
<li>
<a href="" onclick="window.open('http://www.tripadvisor.in/Hotel_Review-g1131922-d4550301-Reviews-Camp_X_Terra_Ranichauri_by_Nature_Connect_Outdoors_Pvt_Ltd-New_Tehri_Uttarakhand.html')" onMouseOver="changeBgImage('images/trip.jpg', 'test')">
<img onMouseOver="changeBgImage('images/trip.jpg', 'test')" src="images/tripadvisor.png" alt="Trip Advisor" title="Trip Advisor" width="40" height="40" />
</a>
</li>