<a href="mailtobama@whitehouse.gov?subject=Congrats%20Obama">obama@whitehouse.gov</a>

I put this in the html tab but when flicking to design tab it gets converted to this:

<A href="mailtobama@whitehouse.gov?subject=Congrats%20Obama">mailtobama@whitehouse.gov?subject=Congrats%20Obama</A>

so it looks messy on the finished page, where the link looks like this:

bama@whitehouse.gov?subject=Congrats%20Obama" href="mailtobama@whitehouse.gov?subject=Congrats%20Obama">mailtobama@whitehouse.gov?subject=Congrats%20Obama

This behavior can be reproduced on your sample on your website.