One of the most important things you need to do when starting to design is understanding who your users are. Resist if you are told to design "for anybody", this way your design will be good for nobody. Choose a target population even if you think that other people will use your site as well. Find out everything you can about your target audience.
In addition, you can consider users computer savvy. Generally people think that users are divided into 2 groups: beginners (people who hardly use computer) and experts (people who are fluent). This is not a realistic division.
A better way to think about it:
1. There are people generally computer savvy.
2. People know how to perform a particular task, for example HR work.
3. People know the particular software, but may not be fluent in other areas.
This type of scale will help you to better position your users.