Use Version History to view previous versions of files stored in OneDrive or SharePoint libraries.

The COUNT function counts the number of cells that contain numbers, and counts numbers within the list of arguments. Use the COUNT function to get the number of entries in a number field that is in a range or array of numbers. For example, you can enter the following formula to count the numbers in the range A1:A20: =COUNT(A1:A20).In this example, if five of the cells in the range contain ...

Note: If you don’t see the Change link, it may be because some information, such as your name, photo, or title, is collected from systems that your IT or human resources department control.If you want to update those details, contact your administrator. If you need help finding your administrator, see How do I find out who my admin is?

Note: If the instructions don't match what you see, you might be using an older version of Outlook on the web.Try the Instructions for classic Outlook on the web.

Learn about certificate errors in Internet Explorer: what they are, what they mean, and what you should do about them.

Contact Microsoft Support. Find solutions to common problems, or get help from a support agent.

Driver updates for Windows 10 and many devices (such as network adapters, monitors, printers, and video cards) are automatically downloaded and installed through Windows Update.

提示: 如果要绕过“文件”>“打开”并始终使用“打开”对话框，请执行此操作：选择“文件 > 选项 > 保存”，然后选择“打开或保存文件时不显示 Backstage”框检查。然后，关闭所有打开的 Office 应用程序再重新打开。 请注意，此更改仅影响按 Ctrl+O 访问“打开文件”对话框时看到的内容。

Get up to speed with Microsoft Office by using these cheat sheets for quick reference and mastering keyboard shortcuts.

Change your password with your email provider. See the following sections for instructions on changing your email account password for several major email providers.