function show_intro(pre,pree, n, select_n,css) 
//                图层id,标题id
{
	for (i = 1; i <= n; i++) 
	{
	var intro = document.getElementById(pre + i);
	var cha = document.getElementById(pree + i);
	intro.style.display = "none";
	cha.className=css + "_on";
	
		if (i == select_n) 
		{
		intro.style.display = "block";
		cha.className=css + "_off";
		}
	}
}
function showhide_intro(pre,pree, n, select_n,css) 
//                图层id,标题id
{
	var intro = document.getElementById(pre + select_n);
	var cha = document.getElementById(pree + select_n);
	intro.style.display=(intro.style.display=="none")?"block":"none";
	cha.className=(cha.className==css+"_on")?css+"_off":css+"_on";
}
function showintro(pre) 
//                图层id,标题id
{
	var intro = document.getElementById(pre);
	intro.style.display="block";
}
function hiddenintro(pre) 
//                图层id,标题id
{
	var intro = document.getElementById(pre);
	intro.style.display="none";
}