Javascript and WordPress

I have an html page that uses JavaScript and the page works fine as a standalone web page. When I open the .htm file on my hard drive, everything works fine. When I open WordPress, and edit an existing WordPress page and using the HTML edit window I paste in all the html code including the JavaScript except leaving out the opening and closing html and body tags. When I open the page on the Internet in my WordPress site, the page works in all Browsers except FireFox. Is there something quirky with WordPress and FireFox and JavaScript that I should know about?