search block form not accepting special characters in drupal 7 If I search with any special character in drupal default search block form it returns error message like "You must include at least one positive keyword with characters or more.".after i do search with letters or numbers it does not bring results.shows same error.the form has been submitted but value does not change.
Any help appreciated..
The error has nothing to do with special characters (e.g. "$", "@"). It pertains to the length of your keywords. By default, Drupal core search restricts minimum keyword size to 3; any query less than 3 characters will trigger the error (e.g. "$9"). 

If you really need search to include 2/1 character queries, the search settings in /admin/config/search/settings under the Minimum word length to index option will allow you to do this.

Note: This will expand out the size of your search index (catching common words like "an" &amp; "a"). If you have a large site with thousands of nodes you shouldn't do this.