function isNullString(string) {
    if (string.length == 0)
            return true;
    else
            return false;
}

function searchcheck() {
    if (isNullString(document.search_text.search_text.value)) {
            alert('ãÀ¸½Ç ³»¿ëÀ» ÀÔ·ÂÇØÁÖ¼¼¿ä.');
            document.search_text.search_text.focus();
            return false;
    }
    else 
    document.search_text.search_text.value = document.search_text.search_text.value;
    return true;
}