run this javascript script in the currently loaded page
public static void ExecuteJavascript(HHTMLBrowser unBrowserHandle, string pchScript) { InteropHelp.TestIfAvailableClient(); using (var pchScript2 = new InteropHelp.UTF8StringHandle(pchScript)) { NativeMethods.ISteamHTMLSurface_ExecuteJavascript(unBrowserHandle, pchScript2); } }