Public Cookies

I'm using these lines:

function tView(Value)
   { 
   if (Value) 
      document.cookie = "FullTreeView=True"; 
   else
      document.cookie = "FullTreeView=False";

   window.location.reload();
   }

To set or reset a cookie within an <a> tag. The question is... how do I get this cookie to work on all the pages of the site. It seems that a cookie on one page is different from "the same" cookie on another page. Am I clear?

Sorry... I didn't know where to post it. As a matter of fact, I'm not yet sure if it's clientside or not. I'm not that into this subjects.

Can you help me anyway? Or tell me where to post this question, please?