Originally Posted by Valloric
If the mimetype file is not the first file and/or is not uncompressed, your epub might not work in all epub-supporting software. Calibre, ADE and Sigil can still handle this, but your epub is still non-conformant and may not work elsewhere.
I am using WinRAR to do this. So when I update the changed files, does it changes things enough to be out of spec?