stuHover = function() {
 var cssRule;
 var newSelector;
 for (var i = 0; i < document.styleSheets.length; i++)
  for (var x = 0; x < document.styleSheets[i].rules.length ; x++)
   {
   cssRule = document.styleSheets[i].rules[x];
   if (cssRule.selectorText.indexOf("LI:hover") != -1)
   {
     newSelector = cssRule.selectorText.replace(/LI:hover/gi, "LI.iehover");
    document.styleSheets[i].addRule(newSelector , cssRule.style.cssText);
   }
  }
 var getElm = document.getElementById("nav").getElementsByTagName("LI");
 for (var i=0; i<getElm.length; i++) {
  getElm[i].onmouseover=function() {
   this.className+=" iehover";
  }
  getElm[i].onmouseout=function() {
   this.className=this.className.replace(new RegExp(" iehover\\b"), "");
  }
 }
}
if (window.attachEvent) window.attachEvent("onload", stuHover);


function changBg_1()
{
  bg1.style.background="url(images/bg_03.jpg)";
  bg2.style.background="";
  bg3.style.background="";
  bg4.style.background="";
  show1.style.display="";
  show2.style.display="none";
  show3.style.display="none";
  show4.style.display="none";
  ShowTable.style.display="none";
}

function changBg_2()
{
  bg1.style.background="";
  bg2.style.background="url(images/bg_03.jpg)";
  bg3.style.background="";
  bg4.style.background="";
  show1.style.display="none";
  show2.style.display="";
  show3.style.display="none";
  show4.style.display="none";
  ShowTable.style.display="";
}

function changBg_3()
{
  bg1.style.background="";
  bg2.style.background="";
  bg3.style.background="url(images/bg_03.jpg)";
  bg4.style.background="";
  show1.style.display="none";
  show2.style.display="none";
  show3.style.display="";
  show4.style.display="none";
  ShowTable.style.display="";
}

function changBg_4()
{
  bg1.style.background="";
  bg2.style.background="";
  bg3.style.background="";
  bg4.style.background="url(images/bg_03.jpg)";
  show1.style.display="none";
  show2.style.display="none";
  show3.style.display="none";
  show4.style.display="";
  ShowTable.style.display="";
}