HTML Form Input - problema la adaugarea unui link

[danP]

<form action="do.php" method="post">
            Nume: <input type="text" name="nume"></input>
            Tip: <input type="text" name="tip"></input>
            Descriere: <textarea name="descriere"></textarea>
            Link: <input type="text" name="link"></input>
            <input type="submit" value="Submit"></input>
</form>

Asta e formularul. In casuta Link trebuie sa se insereze un link cu http. Daca fac asta, scriptul nu mai functioneaza.