     }
 
     private func addCloseButton() {
-        let buttonWidth: CGFloat = 50 * Define.Helper.Ratio.horizontal
-        closeButton = UIButton(frame: CGRect(x: view.frame.width - buttonWidth, y: 0, width: buttonWidth, height: buttonWidth))
-        // TODO: Client will supply icon for button.
-        closeButton.setTitle("Close", for: .normal)
-        closeButton.addTarget(self, action: #selector(closeWebView(_:)), for: .touchUpInside)
+        // Client will supply icon and size for button.
+        let closeButtonWidth: CGFloat = 60 * Define.Helper.Ratio.horizontal
+        let closeButtonFrame: CGRect = CGRect(x: view.frame.width - closeButtonWidth, y: 0, width: closeButtonWidth, height: closeButtonWidth)
+        closeButton = UIButton(frame: closeButtonFrame)
+        closeButton.setTitle(Define.String.close, for: .normal)
+        closeButton.addTarget(self, action: #selector(closeWebView), for: .touchUpInside)
         view.addSubview(closeButton)
     }
 

    // MARK: - Properties
    private var payment: AtoneCon.Payment?
    private var webView: WKWebView!
    fileprivate var indicator: UIActivityIndicatorView!
    private var scriptHandler: ScriptHandler!
    fileprivate var closeButton: UIButton!

    private var handlerScript: String {

        webView.contentMode = .scaleToFill
        webView.autoresizingMask = .flexibleWidth
        view.addSubview(webView)
        webView.loadHTMLString(atoneHTML, baseURL: nil)
        webView.navigationDelegate = self
        webView.uiDelegate = self
