I can add a border to a CALayer in this way:
[webView.layer setBorderColor: [[UIColor colorWithRed:0.6 green:0.7 blue:0.2 alpha:1] CGColor]]; [webView.layer
The border property always add border to 4 sides of your view. You can make your own draw method to draw the border at the bottom of your view.
But, why don't you just add a view above your UIWebView to make it looks like a border?