The problem I have is I would like to automate visual validation of a web page instead of having to do it manually which takes time. I already have automation which is capable of validating functionality but not so good at finding visual bugs such as rendering, font, layout and the lots before customer finds them.

The most important factors for me are; support for visual validation, reduced false negatives, reduce or minimal effort to integrate with existing testing framework and support for cross browser testing and hand held devices.