• The button to change the date of the event reads "Button, gift card, logo, other", this is not descriptive of it's function.
• The search button does not have meaningful alt text and reads as "Addon.messages.search". (Messages)
• The orange box with the number inside of it on a message to alert the user to new messages reads only as the number in the box, not the purpose of the number (messages)
• The text "User", which is located inline with "Type of Event:", is labelled as a button however it does not function as such. (Calendar new event)
• There is an empty button in the date input field.(Calendar new event) iOS
• The description input box does not have a label and is not read by the screen reader(Calendar new event) iOS.

Also review role="button" and check tabindex on them.