edit: I just tried the download agent on a site (http://www.plndr.com) and it's throwing parse errors, and clicking the [x] won't close the output box, but the red portion works.
I now understand the issue with the red portion and the [x]. That will be fixed soon.
For the page, there was a bug with get params, those killed the output inspector. I fixed those now, it should be better able to fetch pages like http://www.plndr.com/product/browse?a=34714&catId=0&version=.... I was able to extract the product names from there in an example page, just a download block and an extract block selecting `.product-cell .product-title`. If you still have problems, would you please comment again, open a bug on https://github.com/pipes-digital/pipes/issues or send me a mail? Kind of crucial to iron the kinks out.
The parse errors are annoying, but I failed silencing them so far. The XML parser is throwing them regardless of try-catch, I don't know why. But they will be just ignored later on: 'View output' should show the pure html (instead of parsed and highlighted XML) instead. That seemed to work fine so far (but might fail in a different browser than those tested...).
For now I added some code to detect the different formatted parse errors in webkit browsers, maybe that catches also yours?
But I'm not very happy with just showing the HTML (though it goes through a formatter at least) in that error case. In the long term the extract block should get a visual element picker to create selectors, then it will matter less, but that's something for later.