string text = "Sit to float
                \n
                \n
                \n"; //Customize this string with your own message

default {

    state_entry() {

        llSetText(text, <1.0, 1.0, 1.0>, 1.0);

       // llSitTarget(<0, 0, 1>,ZERO_ROTATION);
    }

    changed(integer change)
    {
        key av = llAvatarOnSitTarget();

        if (change & CHANGED_LINK)
        {
            if (av) // evaluated as true if key is valid and not NULL_KEY
            {
                llSetText("", <1.0, 1.0, 1.0>, 1.0);

            } else if (llAvatarOnSitTarget()==NULL_KEY) {

                llSetText(text, <1.0, 1.0, 1.0>, 1.0);
            }
        }
    }
}