Receiving this error message When we have tried to access the RSS of wordpress blog:
XML Parsing Error: XML or text declaration not at start of entity / Error on line xxx: The processing instruction target matching” [xX] [mM] [IL] “is not allowed
After a long investigation I have found that trailing blank spaces in few php files of wordPress setup resulted due to editing of theme files is the main reason for this issue. To fix this issue either you need to check with erroreous file and remove unwanted blank space and remove it or check with simple one plugin:
1) Install and activate this plugin:
2) Go to WordPress Admin Area –> Setting -> Fix RSS Feed.
3) Click on the “Fix WordPress RSS Feed” button.