function list(x)
{
var x1,x2;

for(i=1;i<=3;i++)
   {x1=eval("document.all.a"+i);
    if (i==x)
        {if (x1.style.display=="none")
            x1.style.display="";
            else
 x1.style.display="";
}
//否则不显示
else
x1.style.display="none";
}
for(i=1;i<=3;i++)
   {x2=eval("document.all.b"+i);
    if (i==x)
        {if (x2.style.backgroundImage=="url(images/button2.jpg)")
            x2.style.backgroundImage="url(images/button1.jpg)";

            else
 x2.style.backgroundImage="url(images/button1.jpg)";

}
//否则不显示
else
x2.style.backgroundImage="url(images/button2.jpg)";
}
}