Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.1191
diff -u -p -r1.1191 common.inc
--- includes/common.inc	7 Jul 2010 17:00:42 -0000	1.1191
+++ includes/common.inc	8 Jul 2010 18:25:53 -0000
@@ -5732,6 +5732,9 @@ function drupal_common_theme() {
     'form_element_label' => array(
       'render element' => 'element',
     ),
+    'form_error_marker' => array(
+      'render element' => 'element',
+    ),
     'vertical_tabs' => array(
       'render element' => 'element',
     ),
Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.476
diff -u -p -r1.476 form.inc
--- includes/form.inc	7 Jul 2010 17:56:42 -0000	1.476
+++ includes/form.inc	8 Jul 2010 18:25:53 -0000
@@ -1090,7 +1090,10 @@ function _form_validate(&$elements, &$fo
     // An unchecked checkbox has a #value of integer 0, different than string
     // '0', which could be a valid value.
     if (isset($elements['#needs_validation']) && $elements['#required'] && (!count($elements['#value']) || (is_string($elements['#value']) && strlen(trim($elements['#value'])) == 0) || $elements['#value'] === 0)) {
-      form_error($elements, $t('!name field is required.', array('!name' => $elements['#title'])));
+      form_error($elements, $t('<a href="#!field_id">!name</a> field is required.', array(
+        '!field_id' => $elements['#id'],
+        '!name' => $elements['#title'],
+      )));
     }
 
     // Call user-defined form level validators.
@@ -3343,6 +3346,9 @@ function theme_form_element_label($varia
   // If the element is required, a required marker is appended to the label.
   $required = !empty($element['#required']) ? theme('form_required_marker', array('element' => $element)) : '';
 
+  // If the element has an error, append the themeable marker to the label.
+  $error = theme('form_error_marker', array('element' => $element));
+
   $title = filter_xss_admin($element['#title']);
 
   $attributes = array();
@@ -3360,7 +3366,50 @@ function theme_form_element_label($varia
   }
 
   // The leading whitespace helps visually separate fields from inline labels.
-  return ' <label' . drupal_attributes($attributes) . '>' . $t('!title !required', array('!title' => $title, '!required' => $required)) . "</label>\n";
+  return ' <label' . drupal_attributes($attributes) . '>' . $t('!title !required !error', array('!title' => $title, '!required' => $required, '!error' => $error)) . "</label>\n";
+}
+
+/**
+ * Theme an invisible error marker for form elements.
+ *
+ * By default this function outputs the error message, if any, in an invisible
+ * span. This allows screen reader users to identify the fields with errors.
+ * Override this function to provide an alternative error marker, such as
+ * visible error text or an indicator with a tooltip to show the full error.
+ *
+ * @param $variables
+ *   An associative array containing:
+ *   - element: An associative array containing the properties of the element.
+ * @return
+ *   A string with a marker to identify an error, otherwise an empty string.
+ *
+ * @ingroup themeable
+ */
+function theme_form_error_marker($variables) {
+  $element = $variables['element'];
+  // This is also used in the installer, pre-database setup.
+  $t = get_t();
+
+  $output = '';
+  if ($raw_error = form_get_error($element)) {
+    // A simple call to empty() will not cut it here as some fields, like
+    // checkboxes, can return a valid value of '0'. Instead, check the
+    // length if it's a string, and the item count if it's an array.
+    // This is the same logic used when validating #required fields.
+    // @see _form_validate()
+    if ($element['#required'] && (!count($element['#value']) || (is_string($element['#value']) && strlen(trim($element['#value'])) == 0))) {
+      $error = $t('This field is required.');
+    }
+    else {
+      $error = strip_tags($raw_error);
+    }
+    $attributes = array(
+      'class' => array('element-invisible', 'error', 'error-marker'),
+    );
+    $output .= ' <span' . drupal_attributes($attributes) . '>' . $error . '</span>';
+  }
+
+  return $output;
 }
 
 /**
Index: modules/field/tests/field.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/field/tests/field.test,v
retrieving revision 1.33
diff -u -p -r1.33 field.test
--- modules/field/tests/field.test	17 Jun 2010 13:16:57 -0000	1.33
+++ modules/field/tests/field.test	8 Jul 2010 18:25:53 -0000
@@ -1300,7 +1300,7 @@ class FieldFormTestCase extends FieldTes
     // Submit with missing required value.
     $edit = array();
     $this->drupalPost('test-entity/add/test-bundle', $edit, t('Save'));
-    $this->assertRaw(t('!name field is required.', array('!name' => $this->instance['label'])), 'Required field with no value fails validation');
+    $this->assertText(t('!name field is required.', array('!name' => $this->instance['label'])), 'Required field with no value fails validation');
 
     // Create an entity
     $value = mt_rand(1, 127);
@@ -1316,7 +1316,7 @@ class FieldFormTestCase extends FieldTes
     $value = '';
     $edit = array("{$this->field_name}[$langcode][0][value]" => $value);
     $this->drupalPost('test-entity/' . $id . '/edit', $edit, t('Save'));
-    $this->assertRaw(t('!name field is required.', array('!name' => $this->instance['label'])), 'Required field with no value fails validation');
+    $this->assertText(t('!name field is required.', array('!name' => $this->instance['label'])), 'Required field with no value fails validation');
   }
 
 //  function testFieldFormMultiple() {
Index: modules/simpletest/tests/form.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/simpletest/tests/form.test,v
retrieving revision 1.53
diff -u -p -r1.53 form.test
--- modules/simpletest/tests/form.test	2 Jul 2010 12:37:57 -0000	1.53
+++ modules/simpletest/tests/form.test	8 Jul 2010 18:25:53 -0000
@@ -63,7 +63,7 @@ class FormsTestCase extends DrupalWebTes
     $elements['file']['empty_values'] = $empty_strings;
 
     // Regular expression to find the expected marker on required elements.
-    $required_marker_preg = '@<label.*<span class="form-required" title="This field is required\.">\*</span></label>@';
+    $required_marker_preg = '@<label.*<span class="form-required" title="This field is required\.">\*</span>.*</label>@';
 
     // Go through all the elements and all the empty values for them.
     foreach ($elements as $type => $data) {
Index: themes/seven/style.css
===================================================================
RCS file: /cvs/drupal/drupal/themes/seven/style.css,v
retrieving revision 1.57
diff -u -p -r1.57 style.css
--- themes/seven/style.css	5 May 2010 16:41:57 -0000	1.57
+++ themes/seven/style.css	8 Jul 2010 18:25:53 -0000
@@ -263,6 +263,10 @@ div.error {
 div.error p.error {
   color: #333;
 }
+div.error a {
+  color: #fff;
+  text-decoration: underline;
+}
 div.status {
   color: #360;
   background: #cf8;