当我使用基于webview的应用程序并且服务器在iphone sdk中失败时，如何查找404错误原因

     - (void)webViewDidFinishLoad:(UIWebView *)webView
{
    int status = [[[webView request] valueForHTTPHeaderField:@"Status"] intValue];
    if (status == 404) {

    }
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response

- (NSInteger)statusCode

webViewDidFinishLoad

NSCachedURLResponse *resp = [[NSURLCache sharedURLCache] cachedResponseForRequest:webView.request];
NSLog(@"status code: %ld", (long)[(NSHTTPURLResponse*)resp.response statusCode]);

webViewDidFinishLoad()

- (void)webViewDidFinishLoad:(UIWebView *)webview {

    NSCachedURLResponse *urlResponse = [[NSURLCache sharedURLCache] cachedResponseForRequest:webview.request];
    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse*) urlResponse.response;
    NSInteger statusCode = httpResponse.statusCode;
}

NSString *htmlCode = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:loadUrl]];    
if (htmlCode==nil)
    {
        // you can handle here with an alert or any message in webview to load.
    }
    else
    {
        [myWebView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:loadUrl]]];
    }

    [htmlCode release];

- (void)webViewDidFinishLoad:(UIWebView *)webView