Source: Microsoft

Word 2010, Excel 2010, and PowerPoint 2010 include an Accessibility Checker to help you create more accessible content. Accessibility Checker runs automatically while you author your file, identifying areas that might make it challenging for users who have disabilities to view or use it. Through the Accessibility Checker task pane, opened from the Backstage view , you can review and fix potential problems with your content.

Review the how to steps on Microsoft’s Support page.