New Post: Difficulty with XPath to get a single result

I'm not yet very familiar with XPath, but what I'm trying to do shouldn't be this difficult. Basically, I'm periodically checking Google finance to see what the current stock price of a few companies. It's nothing fancy, but I've hit a wall.

When I read the html, I can see the price is kept in a node with the id called 'price-panel'. Should be easy, but I'm getting an error when I try to get the node.

string url = "http://www.google.ca/finance?q="+Symbol;
var getHtmlWeb = new HtmlWeb();
var document = getHtmlWeb.Load(url);

var node = document.DocumentNode.SelectNodes("//[@id='price-panel']");

At this point, the following exception gets thrown:

System.Xml.XPath.XPathException: Expression must evaluate to a node-set.

Taking a quick peek at the HTML from right now, it looks like this:

<div id=price-panel class="id-price-panel goog-inline-block">
<div>
<span class="pr">
<span id="ref_16234934_l">2.70</span>
</span>
<div class="id-price-change nwp">
<span class="ch bld"><span class="chr" id="ref_16234934_c">-0.05</span>
<span class="chr" id="ref_16234934_cp">(-1.82%)</span>
</span>
</div>
</div>
<div>
<span class=nwp>
Aug 17 - Close
</span>
<div class=mdata-dis>
<span class=dis-large><nobr>CVE
data delayed by 15 mins -
<a href="//www.google.ca/help/stock_disclaimer.html#realtime"  class=dis-large>Disclaimer</a>
</nobr></span>
<div>Currency in CAD</div>
</div>
</div>
</div>

It's definitely in there. What am I missing?