id ‘s value must not contain whitespace (spaces, tabs etc.). … Unless you are careful to escape it in the CSS, it won’t be recognised as part of the value of an id attribute.

Can class have spaces?

A class name can’t have spaces. When you have a space-separated string in your class attribute, you’re always giving your element several classes.

Can CSS selectors have spaces?

A space in a CSS selector has very special meaning. It means that the part of the selector that occurs right of the space is within (a child of) the part of the selector to the left.