Editing PowerPoint Accessibility Best Practices (section)

=== Artifacts ===

If an image should be ignored by a screen reader (e.g. decorative photos, logos, etc.) it should be marked as an &ldquo;Artifact&rdquo;. PowerPoint doesn’t provide a means to do this however.  

Any image without alternate text will show as an Error up in PowerPoint’s accessibility checker. 

In order to avoid this, enter a punctuation mark such as a dash character as the alternate text. This will not be read out by a screen reader, but it will not show up as an error in PowerPoint's accessibility report like empty alternate text or a space character would.

==== Best practice on the design level ====

Place objects that are purely decorative in PowerPoint templates. They will then be correctly identified as artifacts. <ref>[http://commonlook.com/user-guide-commonlook-office-ppt/accessibility-guidelines-for-ms-powerpoint/user-guide-commonlook-office-accessibility-guidelines-ms-ppt-alt-text/ Adding Alternative Text in MS PowerPoint] (CommonLook by NetCentric Technologies)</ref>