This is what a Promoted Tweet — aka advertisement — looks like on the Twitter website:
How can you tell?
But wait! How is it Dismissed?
Put your pointer to the right of “Promoted By…” …
… and BAM!
… the secret Dismiss Button is uncloaked. PUNCH that sucker.
Every Dismiss costs an advertiser money. Think of it as making them pay a fine for annoying you!
Don’t Report As Spam. That’s useless.
I don’t know how this works with Twitter clients, just the website.