Magento - tons of debug in system.log, how do I debug?

Question

First of all: I have no idea about how Magento structure works

I have seen this list of error that obviously is pretty useless since I don't understand where I have to look for inside the thousands files I have got:

2014-10-05T10:28:48+00:00 DEBUG (7): <config/>
2014-10-05T10:28:48+00:00 DEBUG (7): <config/>
2014-10-05T10:28:49+00:00 DEBUG (7): <config/>
2014-10-05T10:29:19+00:00 DEBUG (7): <config/>
2014-10-05T10:29:19+00:00 DEBUG (7): <config/>
2014-10-05T10:29:20+00:00 DEBUG (7): <config/>
2014-10-05T10:29:20+00:00 DEBUG (7): <config/>
2014-10-05T10:29:21+00:00 DEBUG (7): <config/>
2014-10-05T10:29:23+00:00 DEBUG (7): <config/>
2014-10-05T10:29:23+00:00 DEBUG (7): <config/>
2014-10-05T10:29:25+00:00 DEBUG (7): <config/>
2014-10-05T10:29:25+00:00 DEBUG (7): <config/>
2014-10-05T10:29:26+00:00 DEBUG (7): <config/>
2014-10-05T10:29:29+00:00 DEBUG (7): <config/>
2014-10-05T10:29:29+00:00 DEBUG (7): <config/>
2014-10-05T10:29:29+00:00 DEBUG (7): <theme />
2014-10-05T10:29:31+00:00 DEBUG (7): <?xml version="1.0"?><customgrid></customgrid>
2014-10-05T10:29:33+00:00 DEBUG (7): <?xml version="1.0"?><jstranslator></jstranslator>
2014-10-05T10:29:33+00:00 DEBUG (7): <?xml version="1.0"?><config></config>

These kind of errors appear both from frontend navigation( 2014-10-05T10:29:23+00:00 DEBUG (7): <config/> ) (every page) and backend navigation(both kind of errors).
So I'm wondering if there is a way to find the exact xml file that generates these reports.
I have seen this lines of code while surfing the web:

header("Content-Type: text/xml");
echo Mage::app()->getConfig()->getNode()->asXml();exit;

But I don't know in which files I have to put this sketch

Answer 1

I had a similar issue. The problem was an old debugging code left in lib\\Varien\\Simplexml\\Config.php method loadString :

if(!$xml){ Mage::log($string); }