What elements on the page can be dynamically changed for groups of users?

Question

User interface

Welcome all!
Is it possible to change the design and functionality of a certain page of the site for different user groups? What elements can be changed?
Example: for boys we show a green background, for girls - pink.
The CRM system will determine the optimal parameters, so we are not talking about manual layout.
What comes to mind:
1. Page background
2. Recommendations bar (what products to recommend)
3. Advertising (what to show)
4. Various pop-up windows
Is it possible to change the sizes, colors of buttons, fonts, text, remove elements altogether, etc.?
Tell me which way to dig. What should the site be written in, how can it be implemented?

Answer 1

It depends very much on a variety of criteria. If only "boys" and "girls" - yes, write on anything, just slip different CSS depending on the criterion. With more criteria, there will be more load, and you can get bored with layout.
About recommendations and advertising - this is generally just a selection according to criteria from the base of goods / advertising. Cope on the idea of ​​any DBMS. But again - you need to look at how many criteria.