I'm sorry you're having trouble with your images. One setting to check is the width as the system will automatically compress any image that is over 800 pixels wide. You can also try increasing the resolution (keeping in mind that the file size can't be larger than 5MB.)
If you'd like to send us an email to social_support(at)constantcontact(dot)com with your username, a reference to this post, and one or two of the jpgs that are getting compressed during upload we'd be happy to further troubleshoot this for you.
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