There are a couple of different ways to include hidden fields and buttons in a Web page form, using the HTML input element with particular "type" attributes or optionally using CSS (Cascading ...

The Blogger Template Designer allows you to insert custom CSS code to change your blog's appearance. You can access the advanced settings ... alter your blog's core HTML design.

A demo of the button and the full CSS code are available on CodePen, so be sure to check it out if you’re interested.