Theme development

Hi. First post. I've looked up Google and forums for an answer and cannot find one so...
I want to print out a custom message in the header section using template.tpl.php when the requested page is not found.

Is there a function or flag I can call from the template.tpl.php to determine if the requested page is found..
Something like drupal_page_found() returning a boolean?

I have created a new theme with following regions defined inside .info file.

Hey guys, new to the drupal scene and coding am enjoying it and eager to learn I have a few questions for anyone kind enough to answer I have managed to fix most my own problems with experimenting with the code by myself and you tubing etc. but have came to a couple road blocks and would appreciate some community support.

On the website I am building I have needed to use image mapping on some of the pages. When I put the mapping code in the body of the page the node background stretches by the same amount as the code. Right now the site is only on my local server and none of the code actually appears on the pages. So, my question is, when the sight is on the host's server will the code be seen as a command and not affect the length of the node background?

Thank you !!

I'm trying to theme the "Recent Comment Block".

My template.php function looks like:

I have a page node template named page--node--content_type_name.tpl.php
when I try calling fields using eg print render($content['field_article_author']); nothing appears , how else can I call this fields ?