JavaScript file doesn't open

Hey, so when i’m trying to open ANY JavaScript it displays an error witch is here → Dropbox - Error - Simplify your life
so what can i do to fix it?

You probably haven’t installed MonoDevelop and it seems you haven’t any external script editor set in the preferences:

Do you know where can i download MonoDevelop from because it is not im my unity folder, and on monodevelop.com i get some other software not monodevelop,

Unity is using a fork of MonoDevelop. The easiest way is probably to install Unity again and choose to install MonoDevelop as well. As far as I know, it is not possible to get Unity’s MonoDevelop alone.