sometimes your browser keeps the "old" files in its memory and needs a good F5 Refresh a few times to clear it.

one way to really get rid of the old one is to delete all the files that go to it, then upload all the new files.

Fine but how do I do it?

in ftp, there should be a visual of your online area and your computer area. select the desired files to delete, delete. select the desired files to upload, upload.