I was making a simple rss reader and for some feeds, I was always getting this error “' ', hexadecimal value 0x1F, is an invalid character. Line 1, position 1.”
finally, I found that, well-formed xml does not allow '0x1F'. The range of well-formed xml is
Char ::= #x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD] |
[#x10000-#x10FFFF]
in my case, it was caused for allowing 'gzip' in the request header.