Could you change the target for the GPX download line so that the HTML validates? Think you can just change from _new to _blank:
It throws this error on W3 HTML validation:
Bad value _new for attribute target on element a: Reserved keyword new used.
A browsing context name or keyword is either any string that does not start with an underscore (_) or a string that case-insensitively matches one of: _blank, _self, _parent, or _top.