The following is a list of mySociety's design principles. This is dedicated to Stef, and was put together as a group on the away weekend in June 2007.
(1) Build services that do one thing really well, but make that one thing work on other people’s sites.
(2) Accessibility is not optional, it is the guidestar of good usability for normal users.
(3) All modern websites should work on mobile phones.
(4) All sites must do what they can to appear high in relevent search listings.
(5) Links should never break
(6) URLs should be short, guessable and hackable when possible.
(7) When building sites that connect with large, bureaucratic institutions, always ensure that your design doesn't involve the institution doing anything new.
(8) Where possible, avoid building sites that nobody wants to use to because they look empty ('empty pub syndrome'). When there is no way of avoiding this, ensure that an empty page always offers something useful for users to do.
(9) Always ask users if they are interested in being put in touch with other users who share similar interests.
(10) Privacy of users' information is paramount, and should be assumed to be 'on' as default, but users should be able to give it up if they consider the trade-off worth it.
(11) Cost per user is powerful way of helping to understand whether a site is worthwhile or not. If the user could have done something more valuable with the money it cost to give them your service, you've failed.
(12) Conversion track where you can, as it will help show you when the above principles are not working 