When Joomla 1.5.x is having the core SEF enabled, it's gonna overwrite .htaccess instructions, like this one:
ErrorDocument 404 /404-oops.html
...where you're gently telling the Apache to redirect nonsense urls to a nice and comprehensively helpful page.
Now, here's the workaround inside Joomla code:

It happened sometime around mid June on a Dreamhost user account, older than three years and bloated with quite some antiquated long forgotten web applications. All of a sudden, every site under the above mentioned unix user was displaying this:

undefined_hacker

on top left of a blank page. D'oh...

We're now gonna skip remembering the hassle of urgent chores moving live sites to newly created, separated unix users, naturally after restoring them from the backups. Because, like any respectable host, Dreamhost is providing a

JP is opening a logo creation contest. Let's go get our designers hats and start some GIMP-ing, Photoshopping, Inkscape-ing, or whatever Adobe-ing.

 

When you're finished, you may want to contact Erik.

 

The JP Digital Impact template. This Joomla template is left aligned, showing as we write only one column to the right side of the main content area. But for those hungry for columns, there's one more right to the left on the right. Ahem, in English here's the order of columns: main content | left | right. All in all, the template comes with 18 positions coded in by default. Allowing a richer display than the current blog-like demo (ro read more details, please click on view demo).

Download it! | View Demo

The JP Pub Theme. FREE to use Joomla! template. Some visitors on the forums were asking about a Joomla template suited for bars', or pubs', websites. Well, well, what's a pub to be for the web? Possibly a community site. This made us think through the glass of beer, while keeping our mind outside of its inner circle, so to say. This JP_Pub theme works well with the following extensions: CBuilder, Kunena Forums, EventList, and many more you may find on extensions.joomla.org.

The GNU/GPL covering the Joomla! core and related coding we've been inserting in jp_pub by Joomla!People.

Download it! | View Demo

The JP Car Kults Theme. FREE to use Joomla! template. Inspired from Gork.net's colorfull theme with new module positions coded in. This theme delivers seven color styles, with seven distinct automotive glitz elements: cars that made a cult of sorts, having each their moments throughout the XX-th century.The GNU/GPL covering the Joomla! core and related coding we've been inserting in jp_car_kults by Joomla!People.

Download it! | View Demo

The JP Finance Theme. FREE to use Joomla! template. Inspired from Template World's XHTML theme for the header and icons menu [parameterized for easy backend within jp_finance]; with sole CSS codelines rounded corners [no images]. The CCPL [Creative Commons Public License] comes with the Temper TW's design elements and goes along with the GNU/GPL covering the Joomla! related coding we've been inserting in jp_finance by Joomla!People.

Download it! | View Demo