I created a master page where i added a listitem , i,e ; 
<li ><a href="#" onclick="fProposal()" id="home" > Home </a> </li>
 
 
function fProposal() {
            debugger;
            document.getElementById("LookupId").href = "/Lookups/Lookups.aspx?Id=LookupId";
        }
 
this in maste page with javascript 
 =======================??????????????===========================Now i want to access this id form a child page and want to add the css proparty.
 
 
i did this one,
  =======================================================
 string v = Request.QueryString["Id"]; 
 // ContentPlaceHolder cph = (ContentPlaceHolder)this.Master.FindControl("ContentPlaceHolder1");
         //   HtmlControl li = (HtmlGenericControl)cph.FindControl(v);
        //    HtmlControl li = (HtmlGenericControl)FindControl("UpdatePanel1");
          //  li.Attributes.Add("class", "active");
            //if (li != null)
            //    this.hide.style.Add("display", "none");
 
this is the child page where i want to change... 
 =============================================================
but it is completely error ...
can any one help me....plz ???