HTML file names

Anything wrong with periods in file names?

[Custodian]

Had a co-worker ask me what characters are safe to use when naming HTML files. Specifically I was asked about periods.

I've never used periods anywhere other than .html. But I have not found and can't think of any valid reasons not too.

Anyone know of any technical, SEO or other reasons not to use periods?

Thanks
Custodian

[mm1220]

howtolearn.php.html

seems to work fine for me with apache2.

I presume apache's clever enough to only look for the final dot?