Single versus double quotation marks in HTML & CSS [duplicate]

Question

Could anyone clarify the difference between single and double quotation marks in HTML5 & CSS.

Here's Google's contradictory use of single quotes in HTML:

<link href='https://fonts.googleapis.com/css?family=Roboto' rel='stylesheet' type='text/css'>

And CSS:

font-family: 'Roboto', sans-serif;

While Bootstrap's documentation practices demonstrate the use of double quoted marks in HTML:

<link rel="stylesheet" href="https://cdn.rawgit.com/twbs/bootstrap/v4-dev/dist/css/bootstrap.css">

And CSS:

font-family:"Helvetica Neue",Helvetica,Arial,sans-serif;

Which practice is the best and why ?

EDIT: Is there any valid reason why Google Fonts decided to use single quotes ?

Cedar

Answer 1

Either are valid, but you probably should stick to a certain style guide. For example, Google's style guide suggest using double quotes for HTML and single quotes for CSS. (Although Google Fonts doesn't follow this exactly)

Gisele

Exactly, I'm quite disturbed by Google's Fonts single quote usage. – Cedar

@vorststoom, would you say you feel ...a disturbance in the fonts? Sorry, couldn't help myself :) – Reformation

Answer 2

There's no best practice, because neither has any affect at all on how the code is parsed. You can deliminate attributes and other strings using ' or " interchangeably.

Barman

Answer 3

Generally, no difference. They are interchangeable.

The only important note is not to use one inside itself.

For example in php:

echo '"hello world"';

Outputs - "hello world"

Or

echo "'hello world'";

Outputs 'hello world'

BUT

echo ""hello world"";

Will throw an error if the " is unescaped, as it's closing that parameter before the contents.

Fortitude

Unrelated to the OP. – Dryad

This is Relevant and Important. – Densmore