In a series consisting of three or more elements, separate each element with a comma.

Microsoft style

You need a hard disk, a VGA monitor, and a mouse.

Not Microsoft style

You need a hard disk, an EGA or VGA monitor and a mouse.

Use a comma following an introductory phrase.

Microsoft style

In Windows, you can run many programs.

Not Microsoft style

In Windows you can run many programs.

If you specify a full date in midsentence, use a comma on each side of the year.

Microsoft style

The February 4, 2003, issue of the New York Times reported that .…

Not Microsoft style

The February 4, 2003 issue of the New York Times reported that .…

Do not join independent clauses with a comma unless you include a conjunction. Online documentation often has space constraints, and it may be difficult to fit in the coordinate conjunction after the comma. In these instances, separate into two sentences or use a semicolon.

Microsoft style

Click Options, and then click Allow Fast Saves.

Click Options; then click Allow Fast Saves. (Only if space is limited.)

Not Microsoft style

Click Options, then click Allow Fast Saves.

Do not use a comma between the verbs in a compound predicate.

Microsoft style

The Setup program evaluates your computer system and then copies the essential files to your hard disk.

The Setup program evaluates your computer system, and then it copies the essential files to your hard disk.

Not Microsoft style

The Setup program evaluates your computer system, and then copies the essential files to your hard disk.

Do not use commas in month-year formats.

Microsoft style

Microsoft introduced Windows 7 in October 2009.

Not Microsoft style

Microsoft introduced Windows 7 in October, 2009.