[jQuery] bug in id selector?

[jQuery] bug in id selector?

Hi everyone,
the attached example-code shows a problem I encountered today (firebug
needed).
If an id-attribute contains dots, like
<p id="test2.3">
jQuery isn't able to find it.
If the dots are replaced by underscores everything works fine.
Afaik there is no limitation for the id which prohibit dots as a used
symbol, so I guess this is a bug or for some reason not wanted?
Cheers