It happened that I worked with an online workbook for classes that I have a subscription for. By mistake I pressed a keyboard shortcut (regrettably I don't remenber it, otherwse I would simply repeat the shortcut), and the content turned by 90 degrees. But not all of the content. The toolbar of the workbook ist still in the same position as it should be. My suspicion is that the workbook simply is a PDF and that only the embedded PDF turned but not the whole browser window? Has anybody an idea of what to do? Thank you!