Hi..
i use (external file) to put some files to my courses
but when upload this courses to moodle and want to download this files i can't and message display that there are error and not find the file
can any one help me in this problem
thank a lot  

This might well be where course lab flips from absolute adressing in development to relative post publication.
Post publication relative adressing will often not find files as it looks from where the module has started as it's base address.
Generaly making references to external files isn't a good idea (external we addresses are slightly more acceptable) especially if they are important to your module.
 

Oh if the files are not on moodle or within the same root folder the browser may consider them to be on a different domain. Basic browser security will stop the download and then the moodle API will return an error