var search_field = document.getElementById("search_field");

function set_search_focus(){if (search_field.value == search_default) search_field.value = "";}
function set_search_blur(){if (search_field.value == "") search_field.value = search_default;}

search_field.value = search_default;
search_field.onfocus = set_search_focus;
search_field.onblur = set_search_blur;