I'm trying to make a form which checks if a certain option is selected from a select tag. Here is my current HTML:

<select onchange=yesnoCheck()>

    <option id=noCheck value=>Valitse automerkkisi</option>

    <option id=noCheck value=lada>Lada</option>

    <option id=noCheck value=mosse>Mosse</option>

    <option id=noCheck value=volga>Volga</option>

    <option id=noCheck value=vartburg>Vartburg</option>

    <option id=yesCheck value=other>Muu</option>

</select>

This is the div element which should become visible after Muu is selected:

<div id=ifYes style=display: none;>

    <label for=car>Muu, mikä?</label> <input type=text id=car name=car /><br />

</div>

And here is the JavaScript I'm trying to use:

<script type=text/javascript>

    function yesnoCheck() {

        if (document.getElementById(yesCheck).checked) {

            document.getElementById(ifYes).style.display = block;

        } else {

            document.getElementById(ifYes).style.display = none;

        }

    }

</script>

But it's not working...