Here is an example of using html inside a shortcode attribute:
[expand title='HTML Title']Here is some content[/expand]
HTML Title
Here is some content
As of 1.8.4 this will no longer work. Instead we need to use the tag attribute:
[expand tag='span' title='Non HTML Title']Here is some content[/expand]
Non HTML Title
Here is some content
Here is a test also using HTML in the swaptitle attribugte
[expand title='HTML Title' swaptitle='Hey Dude']Here is some content[/expand]
HTML Title
Here is some content
Title
Here is some content