// main image array
imgs = new Array();

// preload images for mouse events
function load_image( path, name ) {
  if (document.images) {
    imgs[ name ]      = new Image();
    imgs[ name ].src  = path;
  }
}

// called when mouse enters the button image
function mouse_enter( name ) {
  if ( document.images ) {
    document.menu_icon.src = eval( "imgs[ '"+ name + "_icon' ].src" );
    document.images[ name ].src = eval( "imgs[ '" + name +"_hover' ].src");
  }
}

// called when mouse leaves the button image
function mouse_leave( name ) {
  if ( document.images ) {
    document.menu_icon.src = eval( "imgs[ 'default_icon' ].src");
    document.images[ name ].src = eval( "imgs[ '" + name +"_off' ].src");
  }
}