var browserName = navigator.appName;
var browserVersion = parseInt(navigator.appVersion);
var browser;

if (browserName == "Netscape" && browserVersion == 5) {
  browser = "nn6";
}
else if (browserName == "Netscape" && browserVersion == 4) {
  browser = "nn4";
}

else if (browserName == "Microsoft Internet Explorer" && browserVersion == 4 && navigator.appVersion.indexOf("MSIE 7.0") != -1) {
    browser = "ie7";
}

else if (browserName == "Microsoft Internet Explorer" && browserVersion == 4 && navigator.appVersion.indexOf("MSIE 6.0") != -1) {
  browser = "ie6";                      
}

else if (browserName == "Microsoft Internet Explorer" && browserVersion == 4 && navigator.appVersion.indexOf("MSIE 5.5") != -1) {
  browser = "ie55";            
}

else if (browserName == "Microsoft Internet Explorer" && browserVersion == 4 && navigator.appVersion.indexOf("MSIE 5.0") != -1) {
  browser = "ie5";                      
}

if (browser == "nn4" || browser == "ie55" || browser == "ie5" || browser == "ie6") {
    document.write('<center><div style="color: #FF0000; background-color: #FFFFB2; font-weight: bold; border: 2px solid #FF0000; padding: 1px;">Du verwendest einen veralteten Browser!<br />Bitte aktualisiere auf eine aktuelle Version!') ;
    document.write('<a target="_blank" href="http://www.mozilla-europe.org/de/">') ;
    document.write('<img border="0" alt="Browser: Firefox!" title="Browser: Firefox!"   src="http://sfx-images.mozilla.org/firefox/3.6/80x15_square_blue.png" /></a>') ;
    document.write('</div></center>') ;
}