Ajax HTTP error occured. HTTP Result code: 200 I get Ajax error when I click next button. You can test it here. 

I have found out the problem. It is due to the custom module which I have made. 

&lt;!DOCTYPE html&gt;
&lt;meta http-equiv="X-UA-Compatible" content="IE=edge" /&gt;

&lt;?php

/**
 * Implements hook_block_info().
 *
 * This hook declares what blocks are provided by the module.
 */
function custom_module_block_info()
{
    $blocks['tag_cloud'] = array(
        // The name that will appear in the block list.
        'info' =&gt; t('Custom Moudle'),
        // Default setting.
        'cache' =&gt; DRUPAL_CACHE_PER_ROLE
    );
    return $blocks;
}


When I remove the first two line (Doctype and meta). It works fine. But If I remove first two lines. It doesn't work on IE. I had to insert these two statements to get it working on IE. Now If I keep these two lines, it causes Ajax error, and if not It doesn't work on IE.

Can anyone help?
You can't just add arbitrary HTML at the top of a module file - Drupal runs through a process to theme the page, and you need hook into that.

You have a couple of options:


Override html.tpl.php in your theme, and add the tag to the &lt;head&gt; section manually. This is probably the easiest way.
Use drupal_add_html_head() in your module, e.g.

$tag = $element = array(
  '#tag' =&gt; 'meta', 
  '#attributes' =&gt; array(
    'http-equiv' =&gt; 'X-UA-Compatible',
    'content' =&gt; 'IE=edge',
  ),
);
drupal_add_html_head($tag, 'mymodule:ua_compatibility');



Make sure you pick an appropriate hook to do this in (preprocess_page, etc), don't just add it to the top of the file or it won't work.