With the popup Visual Editor you can edit your post and see how it will show up on the site. Some features:
- Change text style, alignment, color, font and size
- Create ordered and unordered lists
- Use media uploading to upload images and other media
- Insert/edit media, images and links
- Insert special characters
- Insert emoticons
- Use spell checking
- Preview the post
Using the visual editor is optional. By the way, the Visual Editor is the same editor WordPress uses. In fact, the Quick Post Widget plugin uses the very same editor shipped with WordPress with some extra plugins.

Now you can not only post from the sidebar, but also from a page, with immediate visual editing!
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