Ascii, Binary, Auto
Now that you are an expert at FTP, there is a small option you should be aware of. It is the mode of the transfer. This can be set to... ASCII, BINARY or AUTO.
In general, text files should be uploaded in ASCII mode. Files such as html, js, css, php, and so on. Other types of files should be uploaded in BINARY mode. These include files such as images, sounds, video, zips, and so on.
Most FTP programs will have the transfer mode set to AUTO. This is usually safe considering most programs are kept up to date and have a good listing of what type of files are to be sent in their correct mode. Personally, I like to follow the script instructions and set the mode manually just in case my program doesn't know and guesses the wrong mode.
What happens if the wrong mode is used? Simply put, they become corrupt files. They will appear broken or not work.