var StylesheetLink01 = "kttc_01.css";
    var StylesheetLink02 = "kttc_02.css";

    function setStyle() {
      var width, height;
      if(window.innerWidth) {
          width = window.innerWidth;
          height = window.innerHeight;
      }
      else if(document.documentElement.clientWidth) {
          width = document.documentElement.clientWidth;
          height = document.documentElement.clientHeight;
      }
      else if(document.body.clientWidth) {
          width = document.body.clientWidth;
          height = document.body.clientHeight;
      }
      var stylesheetLink = document.getElementById("stylesheetLink");
      var useSmall = (width <= 800 && height <= 600);
      stylesheetLink.setAttribute("href", (useSmall ? StylesheetLink01 : StylesheetLink02));
    }
    setStyle();