Give that middle tr a class of say middle.
So the tr that wraps the area starting with “Come andare…“, give it the class like so:
Now, we can add the following CSS:
background: url(http://www.robertagavioli.it/i-5-segreti/images/mid_bg.png) repeat-y scroll 0 0 transparent;
Will likely require a bit more tweaking, we’ll be here to help.