The default code for this is:
Code:
 <div id="logo"><?php echo '<a href="' . HTTP_SERVER . DIR_WS_CATALOG . '">' . zen_image($template->get_template_dir(HEADER_LOGO_IMAGE, DIR_WS_TEMPLATE, $current_page_base,'images'). '/' . HEADER_LOGO_IMAGE, HEADER_ALT_TEXT) . '</a>'; ?></div>
If you want a different text statement you should change the constant for it and not this reference "HEADER_ALT_TEXT", you can search through the admin > developers tools > to find this constant string