..and which were obvious to make a difference.<p>At the site that I work the following things made a measurable impact on the traffic, user retention and user engagement:<p>1) Make content shareable with social networking sites. A year after we implemented this our daily uniques increased by over 70% and social networks generate now almost 50% of the traffic.<p>2) Create badges for user achievements. After the introduction of badges the amount of user generated content doubled in a month.<p>3) Create a weekly newsletter to registered users who have not visited the site for a week. This is not as clear cut but after this was introduced the number of daily logins have increased by about 10% (could be a measurement error though).<p>4) Make the site load faster.<p>..and which did not make any apparent impact or made surprisingly small one:<p>1) Running banner campaigns asking visitors to register. Registration numbers didn't budge - maybe our banners sucked.<p>2) A feature allowing users to follow the content created by other users ala twitter. A few are really using this feature - maybe we had crappy implementation.<p>3) An invite functionality where users can invite their friends to register at the site. Only 5% of daily registrations come from this feature - I was expecting more.<p>Just in case you are curious, these experiments were conducted at: spoki.lv