For icons that require attribution (http://creativecommons.org/licenses/by/3.0/ http://creativecommons.org/licenses/by/3.0/), what is the general practice for p

For icons that require attribution (http://creativecommons.org/licenses/by/3.0/ http://creativecommons.org/licenses/by/3.0/), what is the general practice for providing that? On each web page they're used, or do you put it on an 'About' page?