Confluence Document Preview is Distorted

[Paul Boyer]

After doing an in-place upgrade from Confluence Server 7.9.3 to Confluence Server 7.13.7 I am observing a strange behavior when previewing changes to a document. When I click the  Preview button from within editor mode the page preview renders incorrectly. The entire page is aligned to the right of the browser window and the resulting preview is inaccurate as to what the published page will eventually look like.

Has anyone else noticed this behavior? Is this a known bug with this build of the Confluence Server LTS? I've tried searching online for any bug reports submitted to Atlassian (or better yet, a resolution), but my efforts have been unsuccessful. 

[Paul Boyer · Accepted solution]

The root cause of the distorted preview was the presence of the text in the header applied to all Confluence pages (as pictured). After removing the site-wide header, the previews then began rendering correctly again.