In magento i was integrated post odata service.after that magento application its showing error ie error on line 1 at column 2: StartTag: invalid element name.http://colors.trayii.com/po.php
What is this po.php file?
If you view source of the page you can see this content:
Seems like a broken page, you'd need to trace back why this is the only thing being outputted. It's unlikely you want this xml output at all.