if (document.images) /// if browser understands document.images object, pre-cache the images ///////
  {
   // about 
   aboutstatic = new Image(301,49)
   aboutstatic.src = "../layout/header/images/navigation/about/nav_aboutic_static.png"
   
   aboutover = new Image(301,49)
   aboutover.src = "../layout/header/images/navigation/about/nav_aboutic_over.png"
   
   
   // software
   softwarestatic = new Image(301,30)
   softwarestatic.src = "../layout/header/images/navigation/software/nav_software_static.png"
   
   softwareover = new Image(301,30)
   softwareover.src = "../layout/header/images/navigation/software/nav_software_over.png"
   
   
   // embedded
   embeddedstatic = new Image(301,30)
   embeddedstatic.src = "../layout/header/images/navigation/embedded/nav_embedded_static.png"
   
   embeddedover = new Image(301,30)
   embeddedover.src = "../layout/header/images/navigation/embedded/nav_embedded_over.png"
   
   
   // game
   gamestatic = new Image(301,32)
   gamestatic.src = "../layout/header/images/navigation/game/nav_gamedev_static.png"
   
   gameover = new Image(301,32)
   gameover.src = "../layout/header/images/navigation/game/game/nav_gamedev_over.png"
   
  
   // design
   gamestatic = new Image(301,27)
   gamestatic.src = "../layout/header/images/navigation/design/nav_design_static.png"
   
   gameover = new Image(301,27)
   gameover.src = "../layout/header/images/navigation/design/nav_design_over.png"
  }
  
  else /// if browser doesn't understand document.images, set the images to "empty" ////////// 
  {
   aboutstatic = ""
   aboutover = ""
   softwarestatic = ""
   softwareover = ""
   embeddedstatic = ""
   embeddedover = ""
   gamestatic = ""
   gameover = ""
   gamestatic = ""
   gameover = ""
  } 


///////// hide link button ///////////////////

/*
function HideLinkbutton(buttonSpan)
{
    document.getElementById(buttonSpan).style.visibility = "hidden";
}
*/   
    
//////// display link button ///////////////  
   
/* 
function ShowLinkButton(buttonSpan) 
{
    document.getElementById(buttonSpan).style.visibility = 'visible';
}
*/