locale.inc uses deprecated elements and attributes

I'd prefer to see the styling done in drupal.css, rather than inline. +1 for the fix, -1 for the implementation.

Better, but where did the CSS go? ;) Furthermore, I like semantic markup better, ie. <em class="locale-untranslated"> instead of using spans.

+1 for the CSS/class solution.

maybe the class "locale-nowrap" could become a more general class "nowrap" as this could be used in more locations, eg in drupal:

modules/statistics.module:        array('data' => format_date($log->timestamp, 'small'), 'nowrap' => 'nowrap'),
modules/statistics.module:        array('data' => format_date($log->timestamp, 'small'), 'nowrap' => 'nowrap'),
modules/statistics.module:      array('data' => format_date($log->timestamp, 'small'), 'nowrap' => 'nowrap'),

"locale-untranslated" is locale.module dependent, so that one is ok.

You have put 'style' => 'nowrap' instead of 'class' => 'nowrap' on all locations. Small thinko I suppose.
If that's fixed => +1 from me.

I'm not sure if this is the right tag for this, but there is a del tag which might be a better alternative to strike. http://www.w3.org/TR/html401/struct/text.html#h-9.4

You can make patchfiles which include multiple files instead of making a zip file which adds an extra step for reviewers.
cvs diff -uF^f misc/drupal.css includes/locale.inc.

"del" is not the right tag here. It is not because the default style for "del" is strike-through that it is "correct" to use it if you replacing something with "style=strikethrough". "del" (and "ins") is for document changes, and only for that. Here the strike-through doesn't mean that.

So a "span", or maybe "em" (you put emphasis on the fact that it is untranslated?) is better.

Commited to HEAD.