So, what exactly is, Super Mario Flash...?
Super Mario Flash is a flash game, where it has a level editor used to create Super Mario levels and show them off to the community!
Also has just a regular adventure mode, when you don't want to create anything, or try out anybody's levels.
Pouetpu-Games, the site where I posted at the top of the page, has a big area just to create a level, post the levels, have it rated, get critic advice, and enjoy.
Feel free to post SMF levels! Just post the level page, not the code. I do not want to clutter this topic!