I've separated this post from its original as the original post is related to content that is no longer available and does not apply to this topic anymore.
Please look over this FAQ and pay attention to the second to last paragraph. For ease of reference I've included the relevant content here.
Keep in mind that some of the Inline Sign-up Form's styles can't be customized
before pasting it into the code of your website; it relies on the styles built into your
website. To change the appearance of the sign-up form beyond the background
and button color, you have to choose a new theme or update the CSS in your
website. Your webmaster or the support for your website builder can also help you
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