Web documents have many of the same elements as print documents but there are some points you need to remember, they frequently move or are removed from a site. They often do not have page numbers, publication dates, or authors. So, it is important to state whatever information you have in your reference list and citation.
APA Sixth Edition
New points in APA 6th Edition are that you do not have to include retrieval dates unless the source material may change over time (e.g., wikis). There is no need to include database information unless the item is an archival document (e.g., discontinued journal, monograph, or dissertation that was not formally published somewhere else).
(American Psychological Association, 2010, p. 192)