This is good, but it took me a full minute to figure out what it meant.  Maybe we could do something like:

    var browserIsIE8 = ( request.headers['user-agent'] ) && ( request.headers['user-agent'].indexOf("MSIE 8.0" ) > -1 );
    var urlIsUnsupportedPage = ( request.url.indexOf("/web/unsupported.html") !== -1 );
    var refererIsUnsupportedPage = ( request.headers.referer && ( request.headers.referer.indexOf( "/web/unsupported.html" ) !== -1 ) );
    if ( browserIsIE8 && !( urlIsUnsupportedPage || refererIsUnsupportedPage ) ) {
        ...
    }