it’s ‘content’, not ‘contents’
it can be either one. “contents” can be used to describe items in a location.
it can’t. contents is a countable noun, hence ‘table of contents’ (describing a list of content). in this use case, there is one piece of content.
no, there are multiple contents (words, images, links) that you can enter in the post box
also why are we arguing about grammar
nope, still one piece of content. the content of the post.
imagine the post box was the table of contents and the words and elements are the contents
the post box isn’t a table of contents? it’s a single idea or subject matter, thus is one piece of content (such as the content of a speech). it’s not hard to understand.