This shortcode uses the built-in WordPress login form function to display a simple login form. You can style the login form using the standard WordPress CSS classes.
The CSS classes are as follows:
If you don’t see your desired results when applying these classes, there are a couple of potential issues. Your theme’s CSS may be interfering, or if your CSS is in your content it may be mangled by WordPress. You can get around the WordPress formatting issue by moving your CSS into your theme’s style.css file, or by using one of the several plugins that allow you to add custom CSS to your pages from the WordPress page/post editor.