This is usually the result of an incorrect edit in one of your language DEFINES.

You need to find instances where HEADER_SEARCH_DEFAULT_TEXT appears in your language php files, and when I use ADMIN>>>TOOLS>>>DEVELOPERS TOOL KIT, I find it appears in TWO of my files.

They are:-

/includes/languages/english/header.php

Line #28 : define('HEADER_SEARCH_DEFAULT_TEXT', 'Enter search keywords here');


/includes/languages/english/your_template/header.php

Line #28 : define('HEADER_SEARCH_DEFAULT_TEXT', 'Enter search keywords here');

If you now call up your copies to see what's appearing in the text strings, you may find you (or someone) has deleted the single quote marks along with the text... eg:

define('HEADER_SEARCH_DEFAULT_TEXT', );

whereas (if you want no phrase to appear) it should be:

define('HEADER_SEARCH_DEFAULT_TEXT', ' ');

To fix, simply make sure your text phrase is between two single quote marks:-

define('HEADER_SEARCH_DEFAULT_TEXT', 'Whatever text you want goes in here');