UIWebView: get attributes from hyperlink clicked

I have html page loaded via UIWebView. If user selects link that looks like:

<a webview="2" href="#!/accounts-cards/<%= item.acctno %>"></a>

I can get href value clicked in UIWebViewDelegate method from NSURLRequest:

webView:shouldStartLoadWithRequest:navigationType:

But how I can get attribute value from this hyperlink (webview="2") assuming that attribute name "webview" determined?