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HTML Entities
Reserved characters in HTML are replaced with character entities.
TML Entities
Some characters are reserved in HTML.
The less than (<) or greater than (>) signs in the text, the browser might mix them with tags.
Character entities display reserved characters in HTML.
A character entity is displayed like this:
&entity_name;
OR
_number;
To display a less than sign (<) we must write: < or <
Non-breaking Space
The non-breaking space:   is a commonly used entity in HTML.
A non-breaking space is a space that does not break into a new line.
Two words separated by a non-breaking space are together. This is useful when breaking the words might be disruptive.
Examples:
10
10 km/h
10 PM
The other use of the non-breaking space is to avoid browsers from truncating spaces in HTML pages.
Writing 10 spaces in the text, the browser will remove 9 of them. To add real spaces to your text, you can use the character entity.