Click the "HTML" button in the post editor toolbar. Tumblr switches the post editor to HTML mode. Scroll to the section of code that contains text or the object that you want to center.

Don’t worry, it’s beyond simple to use. This notepad trick works because of HTML’s “contenteditable” attribute that can turn any part of a web page into an interactive area for editing text.

Open-source framework wraps React and CSS and provides a catalog of components and a theme system for composing user ...