function setBackground(){
      return;
      var body = document.body;
      var html = document.documentElement;

      var height = Math.max( body.scrollHeight, body.offsetHeight, html.clientHeight, html.scrollHeight, html.offsetHeight );
	  var minheight = Math.min( body.scrollHeight, body.offsetHeight, html.clientHeight, html.scrollHeight, html.offsetHeight );
      
	  alert(minheight + ';window innerheight=' + window.innerHeight + ';maxheight=' + height);
	  //if(body.scrollHeight < body.offsetHeight ){
	  //   alert('reset height');
	  //}
  }
  
/*dynamic gradient*/
  var setGradient = (function(){ 
      //private variables; 
      var p_dCanvas = document.createElement('canvas'); 
      var p_useCanvas = !!( typeof(p_dCanvas.getContext) == 'function'); 
      var p_dCtx = p_useCanvas?p_dCanvas.getContext('2d'):null; 
      var p_isIE = /*@cc_on!@*/false; 
      //test if toDataURL() is supported by Canvas since Safari may not support it 
      try{ 
	      p_dCtx.canvas.toDataURL() 
	  }
      catch(err){ 
	      p_useCanvas = false ; 
	  }; 
      if(p_useCanvas){ 
	      return function (dEl , sColor1 , sColor2 , bRepeatY ){ 
		      if(typeof(dEl) == 'string') 
			      dEl = document.getElementById(dEl); 
			  if(!dEl) 
			      return false; 
			  var nW = dEl.offsetWidth; 
			  var nH = dEl.offsetHeight; 
			  p_dCanvas.width = nW; 
			  p_dCanvas.height = nH; 
			  var dGradient; 
			  var sRepeat; 
			  
			  // Create gradients 
              if(bRepeatY){ 
			      dGradient = p_dCtx.createLinearGradient(0,0,nW,0); 
				  sRepeat = 'repeat-y'; 
			  }
			  else{ 
			      dGradient = p_dCtx.createLinearGradient(0,0,0,nH); 
				  sRepeat = 'repeat-x'; 
			  } 
			  dGradient.addColorStop(0,sColor1); 
			  dGradient.addColorStop(1,sColor2); 
			  p_dCtx.fillStyle = dGradient ; 
			  p_dCtx.fillRect(0,0,nW,nH); 
			  var sDataUrl = p_dCtx.canvas.toDataURL('image/png'); 
			  with(dEl.style){ 
			      backgroundRepeat = sRepeat; 
				  backgroundImage = 'url(' + sDataUrl + ')'; 
				  backgroundColor = sColor2; }; 
			  } 
		 }
		 else if(p_isIE){ 
		     p_dCanvas = p_useCanvas = p_dCtx = null; 
			 return function (dEl , sColor1 , sColor2 , bRepeatY){ 
			     if(typeof(dEl) == 'string') 
				     dEl = document.getElementById(dEl); 
				 if(!dEl) 
				     return false; 
				 dEl.style.zoom = 1; 
				 var sF = dEl.currentStyle.filter; 
				 dEl.style.filter += ' ' + ['progid:DXImageTransform.Microsoft.gradient( GradientType=', +(!!bRepeatY ),',enabled=true,startColorstr=',sColor1,', endColorstr=',sColor2,')'].join(''); }; 
			 }
			 else{ 
			     p_dCanvas = p_useCanvas = p_dCtx = null; 
				 return function(dEl , sColor1 , sColor2 ){ 
				     if(typeof(dEl) == 'string') 
					     dEl = document.getElementById(dEl); 
					 if(!dEl) 
					     return false; 
					 with(dEl.style){ 
					     backgroundColor = sColor2; 
					 }; 
					 //alert('your browser does not support gradient effect'); 
      			 } 
			 } 
		  })();