imho, there are four possibilities where the ‘p’ comes from:
a – from one of the theme’s template files; possibly header.php or functions.php;
b – from one of the plugins;
c – from one of the WordPress core files;
d – or your site has been hacked.
a — you can eliminate that by switching to the unedited default theme Twenty Eleven;
if the ‘p’ still shows after the switch, then it is not from the theme’s templates.
b — if the ‘p’ still shows with the default theme, try deactivating all plugins;
– also try resetting the plugins folder by FTP or PhpMyAdmin. Sometimes, an apparently inactive plugin can still cause problems.
c — if the error still persists after the above troubleshooting, consider, in your case, updating your WordPress von 3.1.4 to the latest 3.3.2.
always follow the recommended backup procedures before an update.
d — (unlikely) use a virus checker such as https://sitecheck.sucuri.net/scanner/ to check your site.
