How is the Error Page generated?

[kall]

I ask because my little 'custom greeting' in the navbar doesn't show on error pages, among others.

Given that there is no 'error.php' file, where can I globalise the variable? Or, is there a better way to do it?

[merk]

Im not sure what you're asking, but errors are generated by the function standard_error in includes/functions.php.