I've recently tried to import some source from Gmail, and save it as a text file in Eclipse, but discovered an encoding issue that seemed strangely undocumented online.

When I was trying to save the imported source, I would receive an error message:

"Some characters cannot be mapped using 'Cp1252' character encoding".

It turns out that Gmail is using a wider spread of encoding than usual websites. Simply click on File-> Properties -> Text File Encoding -> and select another encoding format until you hit the right one. In my case it was UTF-8.

Then eclipse will save it!