Works for Joomla 1.5

The 404 error is displayed when the page does not exist. Several reasons for this, the page has been deleted or moved by the webmaster.
In this case Joomla displays a very impersonal error 404 page by default.
I suggest in this tutorial to customize your 404 error page.

In oder to see your site 404 error page:
-Visit an article from your site in your browser, keep this page open.
-In another tab in your browser, go to the backend of your site (administration).
Do Content > Article Manager.

In the articles list, find the one you visited with your browser, and uncheck 'published'.

A red circle with a white cross replaces the green symbol indicating that your item is no longer published.

Return to the page of the article displayed in your browser and refresh the page.

The default Joomla 404 error page appears.

I therefore offer you to replace it by a personalized page, below the Teknikprod 404 error page.
I included links, the site logo and a picture from an old French car Peugeot 404 ( I know, it's a froggy joke, but i like it sorry).

How to proceed?
With an FTP client (I personally use filezilla) right-click at the root of your site and create a new folder 'Page404_teknikprod', of course adapt the name to you.

In this file insert the 404 error page (error404.php) you created with Dreamweaver or other and the pictures.
In my case, inside the file error404.php I indicated an absolute address to my images:
img src = "http://www.teknikprod.com/page404_teknikprod/logo_teknik_prod_200x200.png" for the two pictures of my 404 page.

Get the file 'error.php' located under the following directory www / templates / system / error.php
Delete all its content.
Insert the code below:
<php include ('page404_teknikprod/error404.php');>
Again and you understood it,adapt this code to your site.
Transfer the modified file on line.

At the root of the site get the file '.htaccess' in order to change it.
If you do not have one .htaccess file, create one, many tutorials explaining this procedure.
Once .htaccess is on your hard disc rename it to htaccess (without the dot before h) and open it in a text editor.

Insert the code line below the last line in your htaccess file:
ErrorDocument 404 http://www.teknikprod.com/page404_teknikprod/error404.php
Adapt it to you.

Transfer htaccess file to your site, once placed on your online site rename it .htaccess (by adding the dot before h).

Enjoy

Patrick