There are two main kinds of selectors in CSS: One is base selector like h1, h2, body, table or any existing HTML tags. For instance, the following rule sets all paragraphs (<p> elements) to red:
CSS also allows us to define our own custom …
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions.
Consider email address RFCs:
Look at HTML5 form input element (with type=email) regex pattern: