解决UIWebView无法响应_doPostBack事件问题

 /* 适配webview 网页点击事件 */
   NSDictionary *dictionnary = [[NSDictionary alloc] initWithObjectsAndKeys:
                                 @"Mozilla/5.0 (iPhone; U; CPU OS 4_2_1 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/4.0 Mobile/8C148 Safari/528.16",
                                     @"UserAgent" , nil];
  [[NSUserDefaults standardUserDefaults] registerDefaults:dictionnary];
 /* 适配web