what is the difference between Measurement, Field, and Volume?
Measurement is 1 dimensional Field is 2 dimensional Volume is 3 dimensional
Is HTML is a programming language?
No, Although HTML contains ML (Markup Language) it's not a programming language its only markup text, documents, and image. It's browser programming language which shows a document in a browser.
what is the main reason for learning CSS?
Cascading Style Sheets (CSS) present a static website as a dynamic view. It includes that website many colors and some extra dynamic features which are not possible in HTML language.