// use this to show different .css file if browser version < ie7
// convert all characters to lowercase to simplify testing

    var agt=navigator.userAgent.toLowerCase();

    // *** BROWSER VERSION ***
    var is_major = parseInt(navigator.appVersion);
    var is_minor = parseFloat(navigator.appVersion);

    var is_ie     = ((agt.indexOf("msie") != -1) && (agt.indexOf("opera") == -1));
    var is_ie3    = (is_ie && (is_major < 4));
    var is_ie4    = (is_ie && (is_major == 4) && (agt.indexOf("msie 4")!=-1) );
    var is_ie5    = (is_ie && (is_major == 4) && (agt.indexOf("msie 5.0")!=-1) );
    var is_ie5_5  = (is_ie && (is_major == 4) && (agt.indexOf("msie 5.5") !=-1));
    var is_ie6    = (is_ie && (is_major == 4) && (agt.indexOf("msie 6.")!=-1) );

    var is_ie6down = (is_ie && (is_ie3 || is_ie4 || is_ie5 || is_ie5_5 || is_ie6));

if(is_ie6down)
{
     document.styleSheets[0].disabled=true;
     document.styleSheets[1].disabled=false;
}
else
{
     document.styleSheets[0].disabled=false;
     document.styleSheets[1].disabled=true;
}