That script from dynamic drive was designed to be used with PHP or just regular HTML, and was not considered to be used in ASP.Net, in which your using asp.net objects.
In other words, your using the detail views control, with the appropriate hyperlink control, and the server picks up the "rel" tag as a control property attribute, and not just an A tag attribute, and doesn't know what to do with it.
You could try replacing the hyperlink control with just the plain html version of it
<a href=""></a>
My take on it is that you saw a feature that looked cool, but you don't fully understand how it works, and are not able to incorporate it into your project. That script works for that particular situation, and was written to accommodate those particular needs.
So what is it, it's jquery and javascript that produces a sort of a modal flyout panel from the left, that floats above the current z-index or main surface. The action brings up the panel compressed with no width, and slides out to the left side using panel.slide() animating to the left, and then appending html in the panel to fill in the content, or vice versus.
Yes I could make that work, but it would take me about an 2 hours, and this is voluntary.
In situations like this, it's best to start from scratch, and write your own script, make a panel first and hide it on the right, and write some jquery to show and slide the panel width out to the left. It's just css manipulation on the panel, and a little html appending to it.