function copy_clip() {
    var url = $("#back_info").html();     //需要復制的內容
    var txt = url.substring(url.indexOf(":") + 1, url.length);
    if (window.clipboardData) {
        window.clipboardData.clearData();
        window.clipboardData.setData("Text", txt);
        alert('恭喜，復制成功！');
    } else if (navigator.userAgent.indexOf("Opera") != -1) {
        window.location = txt;
    } else if (window.netscape) {
        try {
            netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
        } catch (e) {
            alert("您的firefox安全限制限制您進行剪貼板操作，請在新窗口的地址欄里輸入'about:config'然后找到'signed.applets.codebase_principal_support'設置為true'");
            return false;
        }
        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);

    }
}