HTML tags are divided into two types:
Container tags that have separate opening and closing tags
Empty tags that are immediately closed after their definition
Read more on: HTML container tag https://www.agernic.com

The basics: headings and paragraphs
In HTML / HTM, each paragraph has to be wrapped in a <p> element, like so:
<p>This is a paragraph, yes pagraph.</p>
Each heading has to be wrapped in a heading element:
<h1>I am the title of the story.</h1>
Read more on: How to add text in HTML / HTM

The font-weight property sets how thick or thin the characters in text should be displayed.
CSS Syntax
font-weight: normal|bold|bolder|lighter|number|initial|inherit;
CSS bold - font-weight property

The opacity property specifies the opacity/transparency of an element.
element { background: rgba(red, green, blue, beta); // CSS property }
The beta parameter is a number between 0.0 (fully transparent) and 1.0 (fully opaque).

The function strlen() returns the length of the given $string.
Syntax:
strlen(string $string );
Read more on: strlen online

If you want to delete a record from any MySQL table, then you can use the SQL command DELETE FROM. You can use this command at the mysql> prompt as well as in any script like PHP.