I am using wsftp to upload my files to the server. I run into this problem case of letters. I accidently named one files with "image.JPG" and "image.jpg" is already on the server. I was able to upload that file to server. I thought it will not allow creating duplicate file name. So the server is case sensitive, that mean "image.jpg =/ image.JPG.
So on the browser address bar I have to type either one of the name with the right case to get the image to show up.