browserversion=navigator.appVersion;

browserversion="0";
if (navigator.appVersion.indexOf("2.")!=-1) {browserversion="2"};
if (navigator.appVersion.indexOf("3.")!=-1) {browserversion="3"};
if (navigator.appVersion.indexOf("4.")!=-1) {browserversion="4"};
if (navigator.appVersion.indexOf("5.")!=-1) {browserversion="5"};
if (navigator.appVersion.indexOf("6.")!=-1) {browserversion="6"}; 
if (navigator.appVersion.indexOf("7.")!=-1) {browserversion="7"}; 

if ((navigator.appName=="Microsoft Internet Explorer") &&(browserversion < 7)) {  
document.write( "<link rel=stylesheet type=text/css href=style/styles_ie6.css>")
}

else  {
document.write( "<link rel=stylesheet type=text/css href=style/styles.css>")
}
if ((navigator.appName=="Microsoft Internet Explorer")) {  
document.write( "<link rel=stylesheet type=text/css href=style/styles_ie_common.css>")
}