Question

A couple of questions concerning this:

• Is it good practice?
• Will it, on a large scale, result in better load times?
• Can it result in browsers ‘breaking’?
• Is the same true for the last function in JavaScript (/jQuery)?

What I mean is stuff like this:

#myElement {
  position: absolute;
  top: 0;
  left: 0
}

Answer 1

Is it good practice?

It’s not good practice to manually exclude semicolons. This is purely because it’s easy to overlook when adding more styles, especially if you’re working in a team:

Imagine you start with:

.foo {
    background-color: #F00;
    color: #000             <-- missing semi-colon
}

And then someone adds some styles:

.foo {
    background-color: #F00;
    color: #000             <-- missing semi-colon
    width: 30px;
    z-index: 100;
}

Suddenly the other developer is wasting time figuring out why their width declaration isn’t working (or worse yet, doesn’t notice that it’s not working). It’s safer to leave the semi-colons in.

Will it, on a large scale, result in better load times?

Most definitely, for every block, you’d save a couple of bytes. These add up, especially for large style sheets. Instead of worrying about these performance gains yourself, it’s better to use a CSS compressor, such as the YUI Compressor to automatically remove the ending semi-colons for you.

Can it result in browsers ‘breaking’?

No, it’s safe, as browsers implement this part of the specification correctly. The CSS2 specification defines a declaration thusly:

A declaration is either empty or consists of a property name, followed by a colon (:), followed by a property value.

More importantly:

…multiple declarations for the same selector may be organized into semicolon (;) separated groups.

This means that ; is used to separate multiple declarations, but it is not needed to terminate them.

Is the same true for the last function in JavaScript?

JavaScript is a whole different beast with a completely different specification. This particular question has been answered in depth many times before on Stack Overflow.