Apostrophes and Quotation Marks
Use the typographic characters (also called smart quotes) for apostrophes and quotation marks.
Note that in Firefox for desktop and Firefox for Android in en-US this rule is enforced programmatically so a developer’s code will be backed out if a text string contains the straight apostrophe or quote.
In the product, use serial commas (also called Oxford commas).
The success of the internet as a public resource depends upon interoperability, innovation, and decentralized participation worldwide.
The success of the internet as a public resource depends upon interoperability, innovation and decentralized participation worldwide.
Hyphens and Dashes
Use hyphens (-) to create a single idea out of two or more words. Don’t add a space before or after the hyphen.
Use en dashes (–) for ranges, like numbers (e.g., 1–9) and dates. Don’t add a space before of after the en dash.
Use em dashes (—) to set related — but separate — thoughts off from each other. Add a space on either side of the em dash.
Use with Button or Menu items when the action requires additional user input, usually via a Dialog, an Alert or moving the operation to another window or part of the UI.
Do not use an ellipsis in a link to indicate that more information is available at the destination.
In general, do not use ellipses in body copy.
Use sparingly, when the text reflects genuine excitement, not as a way to create excitement. Exclamation points aren’t a substitute for creating excitement.
Periods and Other Terminal Punctuation
Terminal punctuation signals the end of a text element. A period is the most common terminal punctuation. Use terminal punctuation at the end of a sentence in normal body copy. In general, do not use punctuation at the end of a headline, button label, checkbox or radio button label, tooltip, text link (unless the link ends a sentence), or navigation element.