UIWebView第三方网站带有自定义样式表

Question

如何向UIWebView添加自定义本地样式表，请求第三方网站如facebook.com。

import UIKit

class ViewController: UIViewController {

    @IBOutlet var WebView: UIWebView!
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        let URL = NSURL(string: "www.any3rdpartywebsite.com" )
        WebView.loadRequest(NSURLRequest(URL: URL!))


    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}