Custom Styles

If I had added some custom styles in the display settings, where would these be stored? In a file or in the DB tables?
Ive been informed that I have some file corruption as every time I log in to my dashboard and do something, something else unrelated either changes or disappears and this time all my custom styles have gone so my header is unstyled and my link to my mint stats plugin has gone so visits have been unrecorded.