png_setup = function() {
    var mainMenu = document.getElementById( 'mainMenu' );
    var mainMenu_objects = document.getElementsByTagName( 'UL', mainMenu );

    if ( navigator.appVersion.indexOf('MSIE 7') != -1 ) return true;

    for ( i = 0; i <= mainMenu_objects.length; i++ ) {
        if ( typeof mainMenu_objects[i] == "undefined" ) break;
        if ( typeof mainMenu_objects[i].currentStyle == "undefined" ) break;

        var current_bg = mainMenu_objects[i].currentStyle["backgroundImage"];

        if ( current_bg.indexOf(".png") != -1 ) {
            mainMenu_objects[i].style.backgroundImage =
                current_bg.replace( /\.png/, ".gif" );
        }
    }

    return true;
}
if ( window.attachEvent ) {
 window.attachEvent( 'onload', png_setup );
}