Hi Patricia!
Accessibility is definitely important. And there's so much to learn about it!
As far as accessibility and web animation goes, animation can both help and hurt accessibility. Animation can help by reducing cognitive load or making things easier to understand or follow. But it can also have some negative implications for folks with vestibular disorders or other conditions.
I wrote about some of the implications for folks with vestibular disorders and what to do about it on A List Apart a while back: alistapart.com/article/designing-safer-web-animat… and I have a whole chapter on animating responsibly in Designing Interface Animation (rosenfeldmedia.com/books/designing-interface-anim…). There is definitely a lot to be considered.
My general advice for animating responsibly is to make sure any animation you use has a defined purpose (branding, UX, etc..), provide meaningful context for large amounts of animation so people aren't ambushed by something they aren't expecting, and give users control whenever possible. Offering some method for reducing animation can be a welcome compromise in cases were large amounts of animation are called for. (http://holohalo.net/ does this well). There are some efforts in the works to make this idea of reducing motion easier which is really great.