Topic on Forum:Trope Talk
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Answering the second question first: You can practice your edits in Sandbox.
As to what Sandbox is and how you can use it: Sandbox is a set of pages that are deliberately kept out of the "Main" space were all the articles are kept. You shouldn't be able to break anything by playing in a Sandbox, so you can use it to try out new markup and new gadgets without affecting anything else.
Each User has his or her own Sandbox. Mine is at User:Robkelk/sandbox - I use it as a place to keep track of my ongoing projects. Yours is at User:Jade Shauni/sandbox