In NS4 its ...

Code:
   with(document.layers[layerID].document){
         open();
         write(txt);
         close();
    }
..but use this function I wrote, Its cross-browser complient...

Code:
    function writeLayer(layerID,txt){
            if(document.getElementById){
                  document.getElementById(layerID).innerHTML=txt;
            }else if(document.all){
                  document.all[layerID].innerHTML=txt;
            }else if(document.layers){
                  with(document.layers[layerID].document){
                        open();
                        write(txt);
                        close();
                  }
            }
      }