I have been asked to reply.
The information requested falls within the responsibility of the Central Office of Information. I have asked the chief executive to reply.
Letter from Alan Bishop, dated December 2008:
As Chief Executive of the Central Office of Information (COI), I have been asked to reply to your recent Parliamentary Question  on what assessment has been made of the accessibility of Government websites.
Standards for websites across government are the responsibility of the Central Office of Information (COI). Guidance on website accessibility was issued to Departments in June 2008 following public consultation. Departments are required to have central government website accessibility plans in place by 1 January 2009. Plans must be implemented and all websites must comply with the double-A W3C web accessibility standard by 1 January 2010. Departments will be requested to report their compliance with these measures.