You should be able to get a reference to the control object which is located in master page from your content page using syntax like this:
HtmlGenericControl yourDiv = this.Master.FindControl("yourDiv") as HtmlGenericControl;
Label yourlbl = this.Master.FindControl("yourlbl") as Label;
However please note that to get a reference to your div control you should be having a runat="server" in the div declaration i.e., it is actually a server side html control.
Regards
Pawan