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

Answer 1

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.

Answer 2

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)

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.