WordPress at a glance
function is not described

wpmu_signup_stylesheet() WP 3.0.0

Prints styles for front-end Multisite signup pages

No Hooks.

Return

Nothing (null).

Usage

wpmu_signup_stylesheet();

Code of wpmu signup stylesheet: wp-signup.php VER 5.1.1

<?php
function wpmu_signup_stylesheet() {
	?>
	<style type="text/css">
		.mu_register { width: 90%; margin:0 auto; }
		.mu_register form { margin-top: 2em; }
		.mu_register .error { font-weight: 600; padding: 10px; color: #333333; background: #FFEBE8; border: 1px solid #CC0000; }
		.mu_register input[type="submit"],
			.mu_register #blog_title,
			.mu_register #user_email,
			.mu_register #blogname,
			.mu_register #user_name { width:100%; font-size: 24px; margin:5px 0; }
		.mu_register #site-language { display: block; }
		.mu_register .prefix_address,
			.mu_register .suffix_address { font-size: 18px; display:inline; }
		.mu_register label { font-weight: 600; font-size: 15px; display: block; margin: 10px 0; }
		.mu_register label.checkbox { display:inline; }
		.mu_register .mu_alert { font-weight: 600; padding: 10px; color: #333333; background: #ffffe0; border: 1px solid #e6db55; }
	</style>
	<?php
}