function imageSwap(fileName) {

	if (is.ie7up) {
		imageSuffix = '.png';
	}
	else if (is.nav6up) {
		imageSuffix = '.png';
	}
	else if (is.opera5up) {
		imageSuffix = '.png';
	}
	else {
		imageSuffix = '.gif';
	}

	imageCode='<img src="'+
	fileName+
	imageSuffix+
	'">';
	document.write(imageCode);

}



function Is ()
{   
    var agt=navigator.userAgent.toLowerCase();

    this.major = parseInt(navigator.appVersion);
    this.minor = parseFloat(navigator.appVersion);

    this.nav  = ((agt.indexOf('mozilla')!=-1) && (agt.indexOf('spoofer')==-1)
                && (agt.indexOf('compatible') == -1) && (agt.indexOf('opera')==-1)
                && (agt.indexOf('webtv')==-1) && (agt.indexOf('hotjava')==-1));
    this.nav2 = (this.nav && (this.major == 2));
    this.nav3 = (this.nav && (this.major == 3));
    this.nav4 = (this.nav && (this.major == 4));
    this.nav4up = (this.nav && (this.major >= 4));
    this.navonly      = (this.nav && ((agt.indexOf(";nav") != -1) ||
                          (agt.indexOf("; nav") != -1)) );
    this.nav6 = (this.nav && (this.major == 5));
    this.nav6up = (this.nav && (this.major >= 5));
    this.gecko = (agt.indexOf('gecko') != -1);

    this.ie     = ((agt.indexOf("msie") != -1) && (agt.indexOf("opera") == -1));
    this.ie3    = (this.ie && (this.major < 4));
    this.ie4    = (this.ie && (this.major == 4) && (agt.indexOf("msie 4")!=-1) );
    this.ie4up  = (this.ie  && (this.major >= 4));
    this.ie5    = (this.ie && (this.major == 4) && (agt.indexOf("msie 5.0")!=-1) );
    this.ie5_5  = (this.ie && (this.major == 4) && (agt.indexOf("msie 5.5") !=-1));
    this.ie5up  = (this.ie  && !this.ie3 && !this.ie4);
    this.ie5_5up =(this.ie && !this.ie3 && !this.ie4 && !this.ie5);
    this.ie6    = (this.ie && (this.major == 4) && (agt.indexOf("msie 6.")!=-1) );
    this.ie6up  = (this.ie  && !this.ie3 && !this.ie4 && !this.ie5 && !this.ie5_5);
    this.ie7    = (this.ie && (this.major == 4) && (agt.indexOf("msie 7.")!=-1) );
    this.ie7up  = (this.ie  && !this.ie3 && !this.ie4 && !this.ie5 && !this.ie5_5 && !this.ie6);

    this.opera = (agt.indexOf("opera") != -1);
    this.opera2 = (agt.indexOf("opera 2") != -1 || agt.indexOf("opera/2") != -1);
    this.opera3 = (agt.indexOf("opera 3") != -1 || agt.indexOf("opera/3") != -1);
    this.opera4 = (agt.indexOf("opera 4") != -1 || agt.indexOf("opera/4") != -1);
    this.opera5 = (agt.indexOf("opera 5") != -1 || agt.indexOf("opera/5") != -1);
    this.opera5up = (this.opera && !this.opera2 && !this.opera3 && !this.opera4);

}
var is;
is = new Is();