The most common cause of feed problems is the content that you post. Many people use word processors, like Microsoft Word, to write up their blog posts – then cut and paste the post into their blogging engine. Sometimes word processors add characters that are very difficult to render in XML. The most likely culprit is the Smart Quote, particularly if you include quotations in your feed posts. Also, Microsoft Word seems to include special tags for formatting paragraphs, as well as address information. While we don't always know where these added characters come from, we do know that when they are introduced, they cause feed processing problems.
You can quickly check if your feed is valid at http://feedvalidator.org.
So how do I keep those unwanted characters out of my feed/blog?
We suggest that you compose your postings in a plain text editor, like Notepad on Windows, or TextEdit on the Mac. You can add HTML tags in your posts, as most blogging engines correctly format those tags for placement inside a feed. Copying from rich-text editors like Microsoft Word can cause invalid characters to appear in your feed.
Can dlvr.it tell me if my feed goes bad?
Sure. You can check your feed’s health with dlvr.it’s Feed Check Up tool. Simply log into your dlvr.it account, open your feed and review the Feed Update tab. We’ll show you a record of the last 72 hours of feed pulls and report any errors we encountered on those feed retrievals. We’ll also send you alerts of critical feed errors if you activate our Service Alerts from your dlvr.it account settings.