rocknbil - 4:59 pm on Mar 5, 2012 (gmt 0)
The "difference" may be due to caching. That is, when you visit a web page, it will cache a copy of the page on your computer, giving the impression of faster browsing. If the browser doesn't recognize it's been changed, it won't reflect the change.
I've given up on styling <hr>. :-) I use a div with a border-bottom instead if it needs to be styled (I know, like using tables for layout . . . but the hr is such a visual only element, I've got bigger battles to fight.)
A FYI, This is XHTML markup
And since you've chosen HTML 4, HTML markup
will make an easier transition to HTML 5, when you are ready.