Index: wp-admin/includes/ms.php
===================================================================
--- wp-admin/includes/ms.php	(revision 21655)
+++ wp-admin/includes/ms.php	(working copy)
@@ -222,12 +222,12 @@
 
 	if ( $current_user->user_email != $_POST['email'] ) {
 		if ( !is_email( $_POST['email'] ) ) {
-			$errors->add( 'user_email', __( "<strong>ERROR</strong>: The e-mail address isn't correct." ), array( 'form-field' => 'email' ) );
+			$errors->add( 'user_email', __( "<strong>ERROR</strong>: The email address isn&#8217;t correct." ), array( 'form-field' => 'email' ) );
 			return;
 		}
 
 		if ( $wpdb->get_var( $wpdb->prepare( "SELECT user_email FROM {$wpdb->users} WHERE user_email=%s", $_POST['email'] ) ) ) {
-			$errors->add( 'user_email', __( "<strong>ERROR</strong>: The e-mail address is already used." ), array( 'form-field' => 'email' ) );
+			$errors->add( 'user_email', __( "<strong>ERROR</strong>: The email address is already used." ), array( 'form-field' => 'email' ) );
 			delete_option( $current_user->ID . '_new_email' );
 			return;
 		}
Index: wp-admin/includes/user.php
===================================================================
--- wp-admin/includes/user.php	(revision 21655)
+++ wp-admin/includes/user.php	(working copy)
@@ -144,7 +144,7 @@
 	if ( empty( $user->user_email ) ) {
 		$errors->add( 'empty_email', __( '<strong>ERROR</strong>: Please enter an e-mail address.' ), array( 'form-field' => 'email' ) );
 	} elseif ( !is_email( $user->user_email ) ) {
-		$errors->add( 'invalid_email', __( '<strong>ERROR</strong>: The e-mail address isn&#8217;t correct.' ), array( 'form-field' => 'email' ) );
+		$errors->add( 'invalid_email', __( '<strong>ERROR</strong>: The email address isn&#8217;t correct.' ), array( 'form-field' => 'email' ) );
 	} elseif ( ( $owner_id = email_exists($user->user_email) ) && ( !$update || ( $owner_id != $user->ID ) ) ) {
 		$errors->add( 'email_exists', __('<strong>ERROR</strong>: This email is already registered, please choose another one.'), array( 'form-field' => 'email' ) );
 	}
Index: wp-includes/ms-functions.php
===================================================================
--- wp-includes/ms-functions.php	(revision 21655)
+++ wp-includes/ms-functions.php	(working copy)
@@ -182,7 +182,7 @@
 
 	if ( ! $user ) {
 		restore_current_blog();
-		return new WP_Error('user_does_not_exist', __('That user does not exist.'));
+		return new WP_Error( 'user_does_not_exist', __( 'The requested user does not exist.' ) );
 	}
 
 	if ( !get_user_meta($user_id, 'primary_blog', true) ) {
@@ -462,7 +462,7 @@
 		$errors->add('user_name', __('Sorry, usernames must have letters too!'));
 
 	if ( !is_email( $user_email ) )
-		$errors->add('user_email', __( 'Please enter a correct email address.' ) );
+		$errors->add('user_email', __( 'Please enter a valid email address.' ) );
 
 	$limited_email_domains = get_site_option( 'limited_email_domains' );
 	if ( is_array( $limited_email_domains ) && empty( $limited_email_domains ) == false ) {
@@ -553,7 +553,7 @@
 		$errors->add('blogname', __( 'Please enter a site name.' ) );
 
 	if ( preg_match( '/[^a-z0-9]+/', $blogname ) )
-		$errors->add('blogname', __( 'Only lowercase letters and numbers allowed.' ) );
+		$errors->add('blogname', __( 'Only lowercase letters (a-z) and numbers are allowed.' ) );
 
 	if ( in_array( $blogname, $illegal_names ) == true )
 		$errors->add('blogname',  __( 'That name is not allowed.' ) );
@@ -590,7 +590,7 @@
 		$path = $base.$blogname.'/';
 	}
 	if ( domain_exists($mydomain, $path) )
-		$errors->add('blogname', __('Sorry, that site already exists!'));
+		$errors->add( 'blogname', __( 'Sorry, that site already exists!' ) );
 
 	if ( username_exists( $blogname ) ) {
 		if ( is_object( $user ) == false || ( is_object($user) && ( $user->user_login != $blogname ) ) )
@@ -956,7 +956,7 @@
 
 	// Check if the domain has been used already. We should return an error message.
 	if ( domain_exists($domain, $path, $site_id) )
-		return new WP_Error('blog_taken', __('Site already exists.'));
+		return new WP_Error( 'blog_taken', __( 'Sorry, that site already exists!' ) );
 
 	if ( !defined('WP_INSTALLING') )
 		define( 'WP_INSTALLING', true );
Index: wp-login.php
===================================================================
--- wp-login.php	(revision 21655)
+++ wp-login.php	(working copy)
@@ -309,7 +309,7 @@
 		$errors->add( 'invalid_username', __( '<strong>ERROR</strong>: This username is invalid because it uses illegal characters. Please enter a valid username.' ) );
 		$sanitized_user_login = '';
 	} elseif ( username_exists( $sanitized_user_login ) ) {
-		$errors->add( 'username_exists', __( '<strong>ERROR</strong>: This username is already registered, please choose another one.' ) );
+		$errors->add( 'username_exists', __( '<strong>ERROR</strong>: This username is already registered. Please choose another one.' ) );
 	}
 
 	// Check the e-mail address