I'm using bootstrap for most of the page, but I'd like to use custom css in a
To reset all the styles for a specific div, you can add the 'all: unset;' CSS property.
<div style="all: unset;">...</div>
This will undo ("unset") all the styles currently applied to that div (but not it's children), leaving you to add which ever ones you desire.
See it in action here (including how to apply to all child elements):
This is a bootstrap accordion that has been "unstyled".
View browser support here: http://caniuse.com/#feat=css-unset-value
Unsurprisingly this doesn't work in IE.