How to make Tidy skip unknown elements (not standard)

Hello guys

I've a simple issue, Im using Tidy via .NET -
everything works great.
But if it hits an element which is not standard and it cannot find that,
it's an fatal error to Tidy and he doesnt go on parsing -
can I ignore this somehow?

Because I'd like to benefit from the rest of the code, even
if one element is <bark> or <marquee>?

cheers
Georg