/* Replace the value of obj by '', except if the value is equal to defval */
function eraseTextField(obj,defval) {
    if(obj.value == defval) {
        obj.value = '';
    }
}

/* Check if a variable is set */
function isset(varname) {
    if (typeof(varname) == 'undefined') {
        return false;
    }
    return true;
}