Styling the default form block

where do I change the css for the default form block?

In your theme you can write new styles to override any core styling.

What you can do is copy the view.php and the view.css from the

concrete/blocks/form

folder and place it into a folder like this

application/blocks/form/templates/customtemplate

you can replace customtemplate with what ever you need make sure you use underscores for spaces _ and all lowercase

then edit the view.css

it goes into it more here