Turn off "code edit mode" before saving

TL;DR: always make sure you switch all rich-text fields away from HTML code editing mode (preferable to Filtered HTML mode) before saving the page.

In Drupal 7, when you have a rich text editing block (one where you can include headers, bold, italic, hyperlinks, etc), you get the option to edit using one of 5 methods:

• Filtered HTML
• Full HTML
• Plain Text
• HTML code
• Display Suite code

What is not at all obvious is that this setting is saved along with the page itself, so that the next person to edit will start in the mode that you used. That would be bad if you're a techie and used HTML code.

But much worse, it turns out that the ability to edit HTML code can be (and by default is) restricted, so that even the page owner can be blocked from editing a field if you've inadvertently saved the page with a field left in HTML code mode.

So don't do that.