Since the release of Joomla 2.5 there has been a particularly annoying “duplicate template” bug that becomes clearly evident when you install or update a template. This has caused a great deal of confusion and consternation among Joomla users, but nobody offered an easy to use fix until recently. As anyone else in this business I hit the wall with this bug, until I found a cure for it on RocketTheme's blog.

With recent upgrade of a great number of servers to PHP 5.3.8 may clients reported that their site began to show error messages like

or

This warning message is produced by PHP if a program attempts to send an additional HTTP header after the separator (and hence all the headers) has already been sent. In the HTTP protocol a server response consists of a group of headers followed by a body, separated by a single blank line (i.e. a line containing only a carriage-return).

A while ago I wrote a tip about problems geting SEF URL's work on 1&1-s servers. Back then I didn't realized, that the problem is the same - or at least fairly similar - on GoDaddy's servers too. Not everywhere, I have a site running on GoDaddy with sh404SEF without any need of tweaking the .htaccess file, but recently I had issues with another site.

So, the trick above solves the problem, but what is the cause?

Joomla generally is running at an acceptable speed -  users aren't seeing differences between an average Joomla site and another CMS'es. But what if they do? What can cause the (sometime unbearable) slowness of some Joomla sites?

After moving a site to a new server I found this error in the backend - at least one error per page, but casually even more.

No error number, no line number... What a heck!