Html session file error

Would this error message appear when somebody tried to edit a past session file ( ie reopening a previous session)? Or is it saying that it cannot open a new session file?

I wish English-speaking developers would write either "the" or "a" instead of saving a small amount of space and making everybody else guess the meaning!

Again, this just a guess, but it just says that the file cannot be written whether it exists or not. This is usually system configuration error.

 Done - documented.