See the APA Publication Manual 6th Edition, pages 180-192 for more on the Reference List.
Identify the color-coded elements to cite web resources on your Reference List:
If no date is specified, put (n.d.) in the year field.
Do not put a period after the URL.
Citations in your paper should be formatted in a black or grayscale font.
If you refer to an entire website, but not a specific document on that site, you only need 
to include an in-text citation and omit it from the reference list.
Example: Kidspsych is a wonderful interactive website for children (http://www.kidspsych.org).
(Adapted from the sixth edition of the APA Publication Manual, © 2010, http://www.apastyle.org/learn/faqs/cite-website.aspx)
If a webpage has no stated author, the title moves to the author field:
(Adapted from the sixth edition of the APA Publication Manual, © 2010, http://www.apastyle.org/learn/faqs/web-page-no-author.aspx)