function copy(txt) {
  if(window.clipboardData) {
    if (window.clipboardData.clearData()) {
      window.clipboardData.setData("Text", txt);
      alert("复制成功！");
    }
  }
  else if(navigator.userAgent.indexOf("Opera") != -1) {
    window.location = txt;
    alert("复制成功！");
  } else if (window.netscape) {
    try {
      netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
    } catch (e) {
      alert("被浏览器拒绝！\n请在浏览器地址栏输入'about:config'并回车\n然后将'signed.applets.codebase_principal_support'设置为’true'");
    }
    var clip = Components.classes['@mozilla.org/widget/clipboard;1'].createInstance(Components.interfaces.nsIClipboard);
    if (!clip)
    return;
    var trans = Components.classes['@mozilla.org/widget/transferable;1'].createInstance(Components.interfaces.nsITransferable);
    if (!trans)
    return;
    trans.addDataFlavor('text/unicode');
    var str = new Object();
    var len = new Object();
    var str = Components.classes['@mozilla.org/supports-string;1'].createInstance(Components.interfaces.nsISupportsString);
    var copytext = txt;
    str.data = copytext;
    trans.setTransferData("text/unicode",str,copytext.length*2);
    var clipid = Components.interfaces.nsIClipboard;
    if (!clip)
    return false;
    clip.setData(trans,null,clipid.kGlobalClipboard);
    alert("复制成功！");
  }
}