Merchants can enable an opt-in e-mail list checkbox for the Shipping Page that customers can check to indicate that they would like to receive e-mail from the store. (The checkbox can be use for some different purpose, but the default text is for an e-mail list.) The [-- Email_List --] tag will produce the checkbox and merchant-defined text. You can test whether the merchant has enabled the option with the [-- IF Email_List --] tag.
The output of the [-- Email_List --] tag does not contain any CSS classes or attributes. You can wrap the tag in an HTML table cell or div or span to apply any additional formatting.
Next: Checkout Custom Fields