// Grabs info about the browser and OS
var agt    = navigator.userAgent.toLowerCase();
var appVer = navigator.appVersion.toLowerCase();

// Determines OS
var is_mac = ( agt.indexOf( "mac"     ) != -1 );
var is_win = ( agt.indexOf( "windows" ) != -1 );

// Determines browser name.
var is_ff  = ( agt.indexOf( "firefox" ) != -1 );
var is_ie  = ( agt.indexOf( "msie"    ) != -1 );
var is_sa  = ( agt.indexOf( "safari"  ) != -1 );

if( is_mac && is_ff ) {
  var obj = document.getElementById('header');
//  obj.style.height = "181px";
  obj.style.height = "138px";
  //alert( "Object = " + obj );
}

if( is_mac && is_sa ) {
  var obj = document.getElementById('header');
//  obj.style.height = "181px";
  obj.style.height = "138px";
}

if( is_win && is_ie ) {
  var obj = document.getElementById('header');
//  obj.style.height = "180px";
  obj.style.height = "137px";
}

if( is_win && is_ff ) {
  var obj = document.getElementById('header');
//  obj.style.height = "180px";
  obj.style.height = "137px";
}