Так сложилось, что recaptchacontrol генерит iframe, поэтому валидацию по doctype
XHTML 1.0 (1.1) Strict не проходит.
Attribute "src" exists, but can not be used for this element.
<iframe src="http://api.recaptcha.net/noscript?k=6LcFSwgAAAAAALDo-5VryV_V7WxE0
Attribute "width" exists, but can not be used for this element.
…ALDo-5VryV_V7WxE0olPdLGaQl6F" width="500" height="300" frameborder="0">
Attribute "height" exists, but can not be used for this element.
…WxE0olPdLGaQl6F" width="500" height="300" frameborder="0">
Attribute "frameborder" exists, but can not be used for this element.
…idth="500" height="300" frameborder="0">
element "iframe" undefined. Did you mean "iframe" or "frame"?
…h="500" height="300" frameborder="0">
Как разрешить эту проблему?