Event.observe(window, 'load', function() {
  Event.observe('search_form', 'focus', clearSearchForm);
  Event.observe('search_form', 'blur', regenerateSearchForm);
});


function clearSearchForm() {
    var search_field = $('search_form')
    if(search_field.value == 'Suchbegriff') {
       search_field.value = '';
    }
}

function regenerateSearchForm() {
    var search_field = $('search_form')
    if(search_field.value == '') {
       search_field.value = 'Suchbegriff';
    }
}