What quality attributes are vital to an ecommerce web application?

This question is just out of interest, and perhaps could be useful for my thesis.

A web application, especially when your business is relying on it financially, needs to meet certain requirements in order to survive. I’d like to hear what kind of (software) quality attributes you find most important (name a few) regarding to web applications.

I give my share:
performance (when visitors have to wait more than 2 seconds, 50% or more will leave your site, meaning less possible sales).

security , atleast be aware of OWASP

reliability, your web app must be able to handle faulty input, but also loads of them.

maintainability, in this world being able to change fast and adapt to your users need to increase sales is vital for survival.