Wikipedia:That's why we preview, kids

Nostradamus, had he been a Wikipedian, would have used the preview button while editing.

Editing a project such as Wikipedia provides many opportunities for good, quality writing. Many times, editors spend hours drafting long, flowing passages describing in intricate detail all of the interesting (and verifiable) facts about their chosen topic. Collaboration on the project's many talk pages helps editors from all over the world come to agreements on how best to improve the project. Many an editor finds a small, forgotten article on some obscure topic and eagerly sets to the task of copyediting.

For every edit that goes as planned, without further modification, there is an edit that is almost immediately undone, redone, or modified. These are the edits that leave whole paragraphs in the tiny text of an unclosed <ref>, or that subsume whole pages of text with that 1000 px thumbnail image.

The preview button stands as a bastion of hope for the meticulous editor.

Hindsight is always 20/20

Once an edit is made and saved by hitting Publish changes, it becomes a permanent record of your contribution to the project. Even if you immediately correct your error, someone, someday, will read it and chuckle. The Preview button permits one to see the future version of the article before it is committed to the ether. If changes are necessary, never fear – the article in its edited form can still be modified before you hit publish.

When committing a previewed edit to the project, editors can be secure in the knowledge that only their best effort will ultimately be the work on which they are ruthlessly judged.

Use of the term in edit summaries

The conscientious editor previews their edits. The truly diligent editor reads through their edits even after committing them to the project by hitting the "Publish changes" button. Despite this, errors creep through - and editors then proceed to immediately correct them. Frequently, they will highlight their error by linking this essay (typically via the shortcut WP:TWWPK). Seeing this shortcut in an edit summary may be viewed as the editor saying "Whoops, look at that, I really should have previewed".

Mistakes help us learn - but making mistakes doesn't mean we need to embarrass ourselves to the entire internet.

wikEd

Enabling wikEd in your Preferences 'Gadgets' section allows you to [among other things] preview edits on the one edit page with no need to reload the page, making it much easier to make any desired changes once you have previewed.