var NN, IE; 

function recognizeBrowser() 
        { NN=false;IE=false; 
          var str = navigator.userAgent; 
          NN = (str.indexOf("Netscape") != -1) ? true : false; 
          if(NN)return; 
          IE = (str.indexOf("MSIE") != -1) ? true : false;} 

function blockMouseIE() 
        { if(event.button == 2){return false;}} 

function blockMouseNN(evt) 
        { if(evt.which == 1){return false;}} 

function blockMouseNN2(evt) 
        { if(evt.which == 3){return false;}} 

recognizeBrowser(); 
          if(NN){document.captureEvents(Event.MOUSEDOWN); document.onmousedown=blockMouseNN; document.onmouseup=blockMouseNN2;}
          if(IE){document.onmousedown=blockMouseIE;}