i just closed a project and when i went to open it it gave me this can you plz help me out thanks
Hang It Up.aup (212 KB)
This FAQ from the Audacity Manual should hep you: http://alphamanual.audacityteam.org/man/Error_Opening_Project:_Reference_to_invalid_character_number_at_line_x
Just be aware that this is the alpha Manual for the as-yet unreleased 2.2.0 version of Audacity - so other pages may/will refer to new stuff. The advice on this page however remains good for 2.1.3 and earlier versions too. I restructured the FAQ for the next release to give clearer advice on errors like this one.
WC
This is actually yet another case of Audacity for Windows not saving supplementary characters properly, a bug that is not even mentioned on the page that you linked to. (Audacity for Windows is saving supplementary characters as pairs of escapes representing surrogates (in the form of 
[89ab][0-9a-f][0-9a-f];
[c-f][0-9a-f][0-9a-f]
when it should be saving them either directly or as five- or six-digit escapes.)
Anyway, TrillDill, I’ve attached a version of your project file that doesn’t contain the supplementary character.
Hang It Up.aup (212 KB)
We do at least have the bug logged now, and (thanks to you Yarn366) we will hopefully not have this bug much longer.
oh wow thank you so much, i was so troubled on that article i got sent your the best 
What’s the exact error message?
Which version of Audacity are you using? (I’m guessing that it’s an old version).
it didnt give me an exact error message this time, but this time it just silenced all my audio on the track, all the gain and panning settings stayed the same it just deleted all sound, im using 2.1.1
I can’t suggest anything without knowing precisely what the error message said (an exact quote of the error message).