var no = 20; // snow number
var speed = 2; // smaller number moves the snow faster
var snowflake = "http://www.gd-edu.net/images/small-1.gif";

var ns4up = (document.layers) ? 1 : 0;  // browser sniffer
var ie4up = (document.all) ? 1 : 0;
var dx, xp, yp;    // coordinate and position variables
var am, stx, sty;  // amplitude and step variables
var i, doc_width = 400, doc_height = 500;
if (ns4up) {
  doc_width = self.innerWidth;
  doc_height = self.innerHeight;
  
} else if (ie4up) {  
  doc_width = 770;//document.body.clientWidth;
  doc_height = 500//document.body.clientHeight;
}
dx = new Array();
xp = new Array();
yp = new Array();
am = new Array();
stx = new Array();
sty = new Array();
for (i = 0; i < no; ++ i) {  
  dx[i] = 0;                        // set coordinate variables
  xp[i] = Math.random()*(doc_width);  // set position variables
  yp[i] = Math.random()*doc_height;
  am[i] = Math.random()*30;         // set amplitude variables
  stx[i] = 0.02 + Math.random()/10; // set step variables
  sty[i] = 0.7 + Math.random();     // set step variables
  if (ns4up) {                      // set layers
    if (i == 0) {
      document.write("<layer name=\"dot"+ i +"\" left=\"30\" ");
      document.write("top=\"15\" visibility=\"hidden\"><img src=\"");
      document.write(snowflake + "\" border=\"0\"></layer>");
    } else {
      document.write("<layer name=\"dot"+ i +"\" left=\"30\" ");
      document.write("top=\"15\" visibility=\"hidden\"><img src=\"");
      document.write(snowflake + "\" border=\"0\"></layer>");
    }
  } else if (ie4up) {
    if (i == 0) {
      document.write("<div id=\"dot"+ i +"\" style=\"POSITION: ");
      document.write("absolute; Z-INDEX: "+ i +"; VISIBILITY: ");
      document.write("hidden; TOP: 15px; LEFT: 30px;\"><img src=\"");
      document.write(snowflake + "\" border=\"0\"></div>");
    } else {
      document.write("<div id=\"dot"+ i +"\" style=\"POSITION: ");
      document.write("absolute; Z-INDEX: "+ i +"; VISIBILITY: ");
      document.write("hidden; TOP: 15px; LEFT: 30px;\"><img src=\"");
      document.write(snowflake + "\" border=\"0\"></div>");
    }
  }
}
var timeoutid
if (document.all) {
layerRef='document.all'
styleRef='.style.'
}
//else if netscape (4.x)
else if (document.layers) {
layerRef='document.layers'
styleRef='.'
} 
else{
alert("你使用的浏览器可能看不到效果。")
}
function show()
{
	
	for (i = 0; i < no; ++ i) {  
		dx[i] = 0;                        // set coordinate variables
		xp[i] = Math.random()*(1000);     // set position variables
		yp[i] = Math.random()*doc_height;
		am[i] = Math.random()*30;         // set amplitude variables
		stx[i] = 0.02 + Math.random()/10; // set step variables
		sty[i] = 0.7 + Math.random();     // set step variables  
	}
	eval(layerRef+'["divTest"]'+styleRef+'visibility="visible"'); 
	eval(layerRef+'["divTest"]'+styleRef+'display="block"');
	eval(layerRef+'["title"]'+styleRef+'visibility="hidden"'); 
	eval(layerRef+'["title"]'+styleRef+'display="none"');	
	begin();
}
function hide()
{
	eval(layerRef+'["title"]'+styleRef+'visibility="visible"'); 
	eval(layerRef+'["title"]'+styleRef+'display="block"');
	eval(layerRef+'["divTest"]'+styleRef+'visibility="hidden"') ;
	eval(layerRef+'["divTest"]'+styleRef+'display="none"') ;	
	end();
}


function snowNS() {  // Netscape main animation function
  for (i = 0; i < no; ++ i) {  // iterate for every dot
    yp[i] += sty[i];
    if (yp[i] > doc_height-50) {
      xp[i] = Math.random()*(doc_width-am[i]-30);
      yp[i] = 0;
      stx[i] = 0.02 + Math.random()/10;
      sty[i] = 0.7 + Math.random();
      doc_width = self.innerWidth;
      doc_height = self.innerHeight;
    }
    dx[i] += stx[i];
    document.layers["dot"+i].top = yp[i];
    document.layers["dot"+i].left = xp[i] + am[i]*Math.sin(dx[i]);
  }
  timeoutid=setTimeout("snowNS()", speed);
}

function snowIE() {  // IE main animation function
  for (i = 0; i < no; ++ i) {  // iterate for every dot
    yp[i] += sty[i];
    if (yp[i] > doc_height-50) {
      //xp[i] = Math.random()*(doc_width-am[i]-30);
      xp[i] = Math.random()*(800-am[i]-30);
      yp[i] = 0;
      stx[i] = 0.02 + Math.random()/10;
      sty[i] = 0.7 + Math.random();
      doc_width = document.body.clientWidth;
      doc_height = document.body.clientHeight;
    }
    dx[i] += stx[i];
    document.all["dot"+i].style.pixelTop = yp[i];
    document.all["dot"+i].style.pixelLeft = xp[i] + am[i]*Math.sin(dx[i]);
  }
  timeoutid=setTimeout("snowIE()", speed);
}

function begin()
{
	for (i = 0; i < no; ++ i)
	{  // iterate for every dot
		//document.all["dot"+i].style.visibility="hidden" ; 
		eval(layerRef+'["dot'+i+'"]'+styleRef+'visibility="visible"');
    } 
	if (ns4up) {
	  snowNS();
	} else if (ie4up) {
	  snowIE();
	}
}

function end()
{
	//alert(timeoutid);
	window.clearTimeout(timeoutid);
	for (i = 0; i < no; ++ i)
	{  // iterate for every dot
		//document.all["dot"+i].style.visibility="hidden"; 
		eval(layerRef+'["dot'+i+'"]'+styleRef+'visibility="hidden"')
    } 
}
function loadpage()
{	
	show();
	timeoutid=setTimeout("hide()", 5000);	
}


document.write("<table border=0 cellpadding=0 cellspacing=0 width='770' align='center'>");
document.write("<tr id=\"title\" style=\"DISPLAY: block; visibility: visible;CURSOR: hand\" onclick=\"javascript:show('divText');\"><td ><img src=\"http://www.gd-edu.net/Images/20040619.gif\"></td></tr>");
document.write("<tr><td id=\"divTest\" style=\"DISPLAY: none; visibility: hidden\" onmouseover=\"javascript:show('divText');\" onmouseout=\"javascript:hide('divText');\">");
document.write("<map name=\"subMap\">");
document.write("  <area shape=\"rect\" coords=\"0,0,770,461\" href=\"http://www.gd-edu.net/help.asp?action=feiyong\" />");
document.write("  <area shape=\"rect\" coords=\"640,458,748,491\" href=\"http://www.gd-edu.net/reg.asp\" target=\"_blank\" />");
document.write("</map>");
document.write("<img src=\"http://www.gd-edu.net/Images/20040620.gif\" border=0 USEMAP=\"#subMap\" />");
document.write("</div>");
document.write("</td>");
document.write("</tr>");
document.write("</table>");
window.onload=loadpage;