This sounds most likely that when you re-zipped the file that you did not get the mimetype file to be uncompressed and to be the first file in the .zip file.
If you are just tweaking a CSS file you will have better luck if instead of re-zip the entire contents you just update the css file that modified. I usually do this by unzipping the .epub file into a new directory (say epub), editing the .css and then updating the .css file in the original .epub. On Mac/*nix this would go like
... finish editing...
zip update ../my.epub stylesheet.css
thank you Jim for replaying so quickly... Im a little confused.....
Im not sure how to get the mimetype file to be first as the files are in this order (when viewed by "Name"):
and in the second part to your response, Im not sure how I just edit the CSS with unzipping and rezipping the entire epub file. yes, Im am on a Mac. perhaps you explain the steps more clearly.
thanks again Jim, I really appreciate the help!
The usual approach to getting the mimetype to be first is to do the mimetype first in one command, and then to do the rest of the files in a second command:
zip -X0 ../my.epub mimetype
zip -rDX9 ../my.epub * -x mimetype
(again these are Mac/*nix based command lines)
And for just editing the CSS the steps I gave above will work as Terminal commands on Mac. Note for me the "edit" command opens the file in BareBones' excellent text editor TextWrangler (which is available for free)
thanks again for replying... I hope you stick with me here... Im still confused. I dont understand Mac based command lines. I zip files by holding down the control key while selecting the epub folder and then selecting the "Create archive of...."
does that help from my end?
Unfortunately to do this correctly, you are going to need to use the Terminal. Or at least I don't know of any 3rd party utilities that'll do this for you, and the built in Mac utilities will not work for this.
Edit: Actually I take that back partially (the bullt in zip utilities are still best used in Termnail). However, you may want to see if eCub helps you out with editing your ePub files: http://www.juliansmart.com/ecub