function proDo(obj){
    var cls=document.getElementById("c"+obj);
    var pro=document.getElementById("p"+obj);
    [bo]if(pro.style.display=="none" || pro.style.display==""){
        pro.style.display="block";[/bo]        cls.style.background="url(../images/jian.gif) no-repeat left center";
    }else{
        pro.style.display="none";
        cls.style.background="url(../images/jia.gif) no-repeat left center";
    }
}

两等号换成一等号

pro.style.display=="none"
就是隐藏的意思了