UX stands for user experience. For a website, it includes how someone understands and completes a task, how the interface responds, and whether the outcome meets their needs. Attractive colors and fonts are only part of that experience.
Follow one complete task
For a learning site, a task might be finding a CSS property, trying its example and adapting the code. Review the whole sequence: can the person choose a relevant lesson, understand the prerequisites, copy a complete example and recognize whether their change worked?
Look for failures and recovery
A search box without useful results breaks the task even if it looks good. An unexplained copy failure leaves the person guessing. A form confirmation that appears before anything was sent creates the wrong expectation.
Exercise: choose a task and observe someone attempting it without instruction. Note where they pause, what they expect and whether they succeed. Ask about their reasoning afterward; do not turn every hesitation into proof of one particular cause.
Improve and check again
Change the explanation or interaction that caused the difficulty, then repeat an appropriate test. Keep the observation and interpretation separate. A shorter page or simpler-looking layout is not automatically a better experience if it removes information the person needs.
Continue with usability testing and UI versus UX.
Sources
Reference 1 provide the technical details and current compatibility information.