Your website design could be triggering migraine attacks.
Is this a trivial issue? Should you care?
There's heaps of information about designing accessible web sites for people with disabilities, because for government agencies in many countries, this is mandatory.
WCAG 2.0 sets guidelines that prevent web sites from starting an epilectic seizure.
But I haven't seen anything in WCAG 2.0 about migraine sufferers, so I'm speaking up on their behalf.