Warning: Invalid argument supplied for foreach() in menu_unserialize() line 400 of includes/menu.inc

Fixed this issue.

Go to your include/menu.inc file and replace the function with the following

function menu_unserialize($data, $map) {
  if ($data = unserialize($data)) {
     	if ((!is_array($data)) && (!is_object($data))) {
         return $data;
         }
    foreach ($data as $k => $v) {
      if (is_int($v)) {
        $data[$k] = isset($map[$v]) ? $map[$v] : '';
      }
    }
    return $data;
  }
  else {
    return array();
  }
}

Editing a core Drupal file is never the right answer to any question. Don't touch.

If you think you have found a bug in core file an issue / bug report and post a patch.

There will most likely be an underlying cause of this issue and the error you are seeing is just a symptom of that. Often it is because some module has not completed all the information that Drupal expects to have.

I would like to know if this error has been fixed in Drupal 7.23.

Nope, neither in Drupal 7.25

These issue is because of your custom module where you implemented hook_menu and created custom menu link and write "access argument" , assigned value of access argument should be an array like 'access arguments' => array(' '),

This appears to be unrelated to webform. If someone can demonstrate instructions to reproduce with webform, where a webform menu item is involved, please feel free to re-open.

#5 solved my issue.

Got same warning #5 works for me

Got same warning #5 works for me

The hook menu item seemed to be throwing the warning here. We got the same warning, using #5 worked for me. I changed

<?php
 'access arguments' => array('access content')
?>

in my menu hook item to

'access arguments' => array(''),

and it removed the warning... not sure why though and this would mean that it would appear if I needed some access restriction.

Any one have an idea?

#5 working for me also.
Thanks nehapandya05

For me, I forgot the array part on 'page arguments' in my implementation of hook_menu().
This was:
'page arguments' => 'ajax_example_dependent_dropdown'
It should be:
'page arguments' => array('ajax_example_dependent_dropdown')