Control working very late...

Hi instead of calling the server to visble the div, you can do in javascript.

for this
after page post .cs file
register the client event
 if (RadioButtonListID.Attributes["OnClick"] == null)
                    RadioButtonListID.Attributes.Add("OnClick", "return showorHidDiv(this,getElementById('" + divmain.ClientID + "'),getElementById('" + divcompany.ClientID + "'));");
                else
                    RadioButtonListID.Attributes["OnClick"] = "return showorHidDiv(this,getElementById('" + divmain.ClientID + "'),getElementById('" + divcompany.ClientID + "'));";

or
foreach(ListItem RadioButton in RadioButtons){
    RadioButton.Attributes.Add("onclick", "showorHidDiv(this,getElementById('" + divmain.ClientID + "'),getElementById('" + divcompany.ClientID + "'))");
}
               

and in the aspx page call the showorHidDiv method like