i need a sheet music site of some sort
 

okay, i don't know if something like this actually exists.

i need like a site where there's an empty staff, and you can pick the tempo, time signature, notes/values etc. and input them, and then it will play like a midi version of the music or something.

because i'm definitely not playing this rhythm right and this hypothetical website would be helpful

There are lots of programs like that, like Sibelius.

Here's a list: http://en.wikipedia.org/wiki/List_of_scorewriters

thanks i'm trying to download sibelius

Sibelius is what I use for my music class. It's really simple when you get used to it.

Plus if I'm composing on guitar I can just write a tab and copy the tab to the stave in Sibelius, transposing it.