After developing a custom portal on Microsoft CRM Portals, I like to share my experience.
This is kind of starter guide to build highly customised web pages on Microsoft CRM portals. It is a high level and very informal guide.
Libraries and frameworks
To customise the portal, a good understanding of followings are essential.
Bootstrap
Microsoft CRM portal uses Bootstrap. Use bootstrap customiser like https://www.bootstrap-live-customizer.com/ for a quick customisation.