There are so many factors available for the success of the website design but Two elements are most important which will help in the web design success :

Need of the user : Many of the time, designers just focus on the client requirements but forget to focus on the user needs too who is the decider of the website success.

Minimal web design : Sometimes, designer use so many elements on the webpage/website which confuse visitors many of the time so always try to design simple but interactive website with minimal element.