Something that can give you such a headache, like subtitles that are out-of-sync, can be fixed from the main window of the program by simply adjusting the time that you'd like to delay or advance the subtitles (down to the millisecond).
You'll find various modes available to edit subtitles. You can do it with just the text in front of you, writing normally and adjusting times, or with the video playing to check and make sure that the images are synching with your words.
Subtitle Edit is an extremely useful program for any fan who wants to see movie and TV series in their original language. Since synching errors are very common with subtitles on the web, this program comes in handy to correct them quickly and painlessly.