Agile web Development with Rails section 9.3

I am reading Agile Web D. with rails (third addition).
And I need some help with it.
I have reached chapter 9.3 (AJAX)

when I press on the add to cart button I get an error message.
a real ugly one.

eventually, I downloaded the PDF version and copied the content of the
files but it did not help.

I have looked but could not find the problem.
Please give me a hand.

the files of this application are at:
Download link:


I think that the error is written in javascript
and this is it:

try {
Element.update(“cart”, "\n\n<div class="cart-title">Your

\n \n\n\n\n\n <tr
id="current_item"> \n\n\n\n\n\n\n\n

\n \n \n\n\n\n \n \n \n \n\n
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\n"); $("current_item").visualEffect("highlight", {"endcolor":"#114411","startcolor":"#88ff88"}); } catch (e) { alert('RJS error:\n\n' + e.toString()); alert('Element.update(\"cart\", \"\\n\\n
Your Cart
\\n\\n \\n\\n\\n\\n\\n \\n\\n\\n\\n\\n\\n\\n\\n \\n \\n \\n\\n\\n\\n \\n \\n \\n \\n\\n
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Total $209.65
\\n\");\n$(\"current_item\").visualEffect(\"highlight\", {\"endcolor\":\"#114411\",\"startcolor\":\"#88ff88\"});'); throw e }