<input class="Form" name="altro1" type="checkbox" value="1" ONCLICK="document.all.mostraBox.style.display = (document.all.mostraBox.style.display == 'none') ? '' : 'none'">

<INPUT TYPE="text" name="categoria" STYLE="display:none" ID="mostraBox" size=24 maxlength="22" class="specialForm" value="Indicare quali">