Wrap HTML with DIV until next H3

Answer 1

An approach like this should work, though I'm guessing there are many different ways of doing this:

$('#subgroup h3').each(function() {
    $(this).nextUntil('h3').wrapAll('<div></div>');
});

Answer 2

This is what it looks like after some nice (and dirty) jQuerying, to tidy up the HTML:

<div id="subgr-productlist">

    <h3>Serie 1000</h3>
    <a id="product-PROD79" href="/global/hygiene/touchfree-dispensers/dispensers/products.aspx?ProductId=PROD79" name="product-PROD79">Model 1010</a>
    <a id="product-PROD80" href="/global/hygiene/touchfree-dispensers/dispensers/products.aspx?ProductId=PROD80" name="product-PROD80">Model 1020</a>
    <a id="product-PROD81" href="/global/hygiene/touchfree-dispensers/dispensers/products.aspx?ProductId=PROD81" name="product-PROD81">Model 1030</a>
    <a id="product-PROD82" href="/global/hygiene/touchfree-dispensers/dispensers/products.aspx?ProductId=PROD82" name="product-PROD82">Model 1040</a>
    <a id="product-PROD83" href="/global/hygiene/touchfree-dispensers/dispensers/products.aspx?ProductId=PROD83" name="product-PROD83">Model 1050</a>

    <h3>Serie 2000</h3>
    <a id="product-PROD234" href="/global/hygiene/touchfree-dispensers/dispensers/products.aspx?ProductId=PROD234" name="product-PROD234">Model 2010</a>

    <h3>Serie 3000</h3>
    <a id="product-PROD85" href="/global/hygiene/touchfree-dispensers/dispensers/products.aspx?ProductId=PROD85" name="product-PROD85">Model 3010</a>

    <h3>Serie 4000</h3>
    <a id="product-PROD86" href="/global/hygiene/touchfree-dispensers/dispensers/products.aspx?ProductId=PROD86" name="product-PROD86">Model 4010</a>
    <a id="product-PROD87" href="/global/hygiene/touchfree-dispensers/dispensers/products.aspx?ProductId=PROD87" name="product-PROD87">Model 4020</a>
    <a id="product-PROD88" href="/global/hygiene/touchfree-dispensers/dispensers/products.aspx?ProductId=PROD88" name="product-PROD88">Model 4030</a>
    <a id="product-PROD89" href="/global/hygiene/touchfree-dispensers/dispensers/products.aspx?ProductId=PROD89" name="product-PROD89">Model 4040</a>

</div>

In other words, all the other a elements disappear?

Then I run this jQuery script:

$('#subgr-productlist h3').each(function(){
    $(this).nextUntil('h3').wrapAll('<div class="test"></div>');
});

But that results in the #subgr-productlist div to render like this:

<div id="subgr-productlist">
    <h3>Serie 1000</h3>
    <h3>Serie 2000</h3>
    <h3>Serie 3000</h3>
    <div class="test">
        <a id="product-PROD85" href="/global/hygiene/touchfree-dispensers/dispensers/products/products.aspx?ProductId=%20Model%203010" name="product-PROD85"></a>
    </div>
    <h3>Serie 4000</h3>
</div>