How much time has passed from the initial idea to its implementation? Most often it is a lot of time, which can be divided into three stages: The emergence of the idea => Design idea as a model => Practical implementation. I propose to focus on the second and third steps. Often a good idea has not leading to implementation is due to a poor study of the main ways for implementation. Losing a good idea or its underestimation can been critical.
Speed and reliability testing (load / stress / performance testing). This test helps to check a behaviour of websites (or its parts) at the same time with an influx of a lot of users. Poor performance (speed) - this is the main issue of many Internet projects. You can build really cool useful site, but low performance could decreased all your achievements.