Prepare!

document.addEventListener("load",
  function(e) {
    if (!document.body) document.body = document.getElementsByTagName("body")[0];
    if (!document.body) return;
    if (!document.links) return;
    for (var i = 0; i < document.links.length; i++) {
      var href = document.links[ i ].getAttribute("href");
      if (!href) continue;
      if (!href.match(/\.pdf$/) &&
          !href.match(/\.doc$/) &&
          !href.match(/\.xls$/))
          continue;

      if (!document.blankIframeHandler) {
        document.blankIframeHandler = document.createElement("iframe");
        with (document.blankIframeHandler) {
          setAttribute("src", "about:blank");
          setAttribute("id", "blankIframeHandler");
          setAttribute("name", "blankIframeHandler");
          setAttribute("style", "display:none;visibility:hidden;");
        }
        document.body.appendChild(document.blankIframeHandler);
      }
      document.links[ i ].setAttribute("target", "blankIframeHandler");
    }
  }, false);