public void AddScriptSource(string filename)
{
Debug.Assert(!InvokeRequired);
if (!RobustFile.Exists(Path.Combine(Path.GetDirectoryName(_url), filename)))
throw new FileNotFoundException(filename);
GeckoDocument doc = WebBrowser.Document;
var head = doc.GetElementsByTagName("head").First();
GeckoScriptElement script = doc.CreateElement("script") as GeckoScriptElement;
script.Type = "text/javascript";
script.Src = filename;
head.AppendChild(script);
}