I do not remember, maybe I already reported this bug but I do not think so . Anyway:

If you have enabled DebugRedirect and in the pagelayout you are requesting, say CSS file which does not exist, for example:

{"stylesheets/not_existing_file.css"|ezdesign}

you may run in big troubles. When you are for example editing the object 32, version 3 and you are going to publish it, you will get back to the page content/edit/32/3 where you have the button "Redirect". Your browser requests stylesheet: content/edit/32/stylesheets/not_existing_file.css (have a look to the source of the generated page if you do not believe), which is processed by edit.php and which creates a new draft of the object 32. So you've got something what was not wanted. In this example it is not so critical, but there may be other redirection pages, where it may be critical.

Proposal of the solution: ezdesign (and other url operators) will return dummy ABSOLUTE path when requested file does not exist, instead of returing the input without change (which is not even quoted). For example
{"stylesheets/not_existing_file.css"|ezdesign}

could return "/not_existing_file". Or it would be even better to have one empty file, the path of which we would return in such a case.

P. S. Same goes with images, JS files. The fact I used enabled DebugRedirect in the example is not important.

Homework: Think about including

{"path/to/not/existing/image.jpg"|ezimage}

in your pagelayout and its consequences.
When you are not using nice urls, think about the session variable LastAccessURI as well.