Years ago, when I was a student, the professor said that it was important to match the requirements of the project and don’t loose time in implementing things not required by the client.
Years later, in my developer life I’ve learned that matching the clients requirements is crucial to keep the costs low, especially in small web agencies, or as a freelancer, where budgets are often low.
Sometimes the developer starts to implement features not required by anybody, I love my work and I know that it happens, you want to make something better, you think it will be useful maybe for another project, and so you start making unnecessary code.
Sometimes it is a Designer or an Account manager of your agency that asks you to change something, to fix those pixels before the client has seen the job, thinking that they only know the client’s opinion.
But the opinion of the client is crucial and almost always it’s the only important opinion to complete the project profitably.
We can represents different situation with Venn’s Diagrams.

As you can see:
A = the set of all the features implemented in the software
B = the set of all the features requested by the client
C = A ∩ B = the set of the features developed and desired by the client, the bigger is C the happiest is the client (and the web agency)

A bad project where clients requirements poorly match the developer work. If this happens and you are the developer, you (or your web agency) really have to improve your ability to listen to the customer.

Quite perfect! You have developed only the things requested, the client is happy, you don’t have loose your time around unnecessary features.

This is a normal project: you had to deal with designers and accounts, you’ve followed pixel perfect problems, and you have also developed things not requested by the client but that you think are important. Maybe the client is not totally happy or maybe he didn’t notice the missed requests, and if you have some soft skills you gained the promise of a “phase 2” for your project.
Cross your fingers.
This story was also published on Medium.