Clearing cache and cookies is a normal maintenance for browsers. Any time your browser gets full of history, odd things can happen such as alignment being off, check boxes looking odd and other things. Also, it is important to do anytime there is a change to a program in order to see any changes that have taken place.

For Safari users, please follow the screenshot in the link.

http://screencast.com/t/OKNnag7mIIb