The program Beyond Compare helps you to do this easily and efficiently. This tool compares folders and files from separate computers and detects differences between the two in order to easily sync folders.
The program also lets you compare files on an FTP and supports the use of filters to do very specific comparisons.
In addition, Beyond Compare includes a very simple text editor that's perfect for modifying programming files without having to use other external applications. You can also customize the flagged differences between the files with certain colors or highlighting.