A course with an example of developing an interactive site for learning?

Question

css

Have you come across examples of developing an interactive site, such as codeacademy, javarush, htmlacademy. And then mostly shops, blogs, forums.

Answer 1

htmlbook.ru/html/legend

<fieldset>
    <legend>Круглосуточная поддержка</legend>
    <p>Любые вопросы, пожелания...</p>
</fieldset>

Many times it was:
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How to make such an element correctly?
Gap with text at block border level?
How to properly style h1 with CSS?