if ((browser.isIE55 || browser.isIE6x) && browser.isWin32) {
	var strExt = ".gif";
// else, if the browser can display PNGs normally, then do that. that list includes:
	//     -Gecko Engine: Netscape 6 or Mozilla, Mac or PC
	//     -IE5+ Mac (OpacityObject applies the background image at 100% opacity)
	//     -Opera 6+ PC
	//     -Opera 5+ Mac (Doesn't support dynamically-set background images)
	//     -Opera 6+ Linux 
	//     -Omniweb 3.1+ 
	//     -Icab 1.9+ 
	//     -WebTV 
	//     -Sega Dreamcast
} else {
	var strExt = ".png";
}