Mihai Parparita: Here are the top XML errors that we have encountered when parsing all of the feeds that our users have added to Reader.
| % of errors | Error description |
|---|---|
| 15.6% | Input claims to be UTF-8 but contains invalid characters. |
| 14.9% | Opening and ending tags mismatch |
| 13.9% | An undefined entity is used (e.g. in an XML document without importing the HTML set) |
| 7.8% | Documented expected to begin with a start tag, but no < was found |
| 5.7% | Disallowed control characters present |
| 5.5% | Extra content at the end of the document |
| 4.2% | Unterminated entity reference (missing semi-colon) |
| 4.2% | Unquoted attribute value |
| 3.8% | Premature end of data in tag (truncated feed) |
| 3.3% | Naked ampersand (should be represented as &) |
| 2.1% | XML declaration allowed only at the start of the document |
| 1.8% | Namespace prefix is used but not defined |
| 0.75% | Comment not terminated |
| 0.64% | Attribute without value |
http://googlereader.blogspot.com/2005/12/xml-errors-in-feeds.html
Randy: Some interesting data would be the percentage chance that a feed has ill-formed XML based on the generator (Blogger, Wordpress, Typepad, MT, etc). Anybody got that data?
Randy