var preloaded = [];

		// here is a lame preloading script i am putting in just for demonstration
		for (var i = 1; i <= 5; i++) {
			preloaded[i] = [loadImage(i + "-0.gif"), loadImage(i + "-1.gif")];
		}

		function init() {
			// whatever stuff you need to do onload goes here.

			//==========================================================================================
			// if supported, initialize mtdropdowns
			//==========================================================================================
			// Check isSupported() so that menus aren't accidentally sent to non-supporting browsers.
			// This is better than server-side checking because it will also catch browsers which would
			// normally support the menus but have javascript disabled.
			//
			// If supported, call initialize() and then hook whatever image rollover code you need to do
			// to the .onactivate and .ondeactivate events for each menu.
			//==========================================================================================
			if (mtDropDown.isSupported()) {
				mtDropDown.initialize();

				// hook all the image swapping of the main toolbar to menu activation/deactivation
				// instead of simple rollover to get the effect where the button stays hightlit until
				// the menu is closed.
/*				menu1.onactivate = function() { swapImage("button1", preloaded[1][1].src) };
				menu1.ondeactivate = function() { swapImage("button1", preloaded[1][0].src) };

				menu2.onactivate = function() { swapImage("button2", preloaded[2][1].src) };
				menu2.ondeactivate = function() { swapImage("button2", preloaded[2][0].src) };

				menu3.onactivate = function() { swapImage("button3", preloaded[3][1].src) };
				menu3.ondeactivate = function() { swapImage("button3", preloaded[3][0].src) };

				menu4.onactivate = function() { swapImage("button4", preloaded[4][1].src) };
				menu4.ondeactivate = function() { swapImage("button4", preloaded[4][0].src) };

				menu5.onactivate = function() { swapImage("button5", preloaded[5][1].src) };
				menu5.ondeactivate = function() { swapImage("button5", preloaded[5][0].src) };
*/


			}
		}

		// this is a crappy example preloader. Use whichever one you want.
		function loadImage(sFilename) {
			var img = new Image();
			img.src ="/_images/nav/" + sFilename;
			return img;
		}

		// this is a crappy example image swapper. Use whichever you want.
		function swapImage(imgName, sFilename) {
			document.images[imgName].src = sFilename;
		}
		
		
var speed = 50;         //速度
var max_opacity = 100;   //最大
var min_opacity = 20; //最小
var do_step   =   5;       //变化的幅度

function change_opacity(obj,do_option)
{
   if(obj.doing)
    clearInterval(obj.doing);
   obj.doing = setInterval(do_option+"_alpha("+obj.sourceIndex+")",speed); 
}


function down_alpha(obj_index)
{
   var obj = document.all[obj_index];
  
   if(obj.filters.Alpha.Opacity > min_opacity )
   {
    obj.filters.Alpha.Opacity += -do_step;
   } 
   else
   { 
    clearInterval(obj.doing);
    obj.filters.Alpha.Opacity = min_opacity;
    obj.doing = false;
   } 
} 
function up_alpha(obj_index)
{
   var obj = document.all[obj_index];
  
   if(obj.filters.Alpha.Opacity<max_opacity)
    obj.filters.Alpha.Opacity += do_step;
   else
   { 
    clearInterval(obj.doing);
    obj.filters.Alpha.Opacity = max_opacity;
    obj.doing = false;
   } 
}