how to 'insert' a reply
If you're using the 'Post a Reply' box at the bottom of the page, it'll add the reply to the end of the thread. If you want to reply to a specific reply within the thread, you need to hit the 'reply' button on that post -- it's in the line with the author's name, all the way to the right. That should open up a new 'reply' field that you can use to respond.
Firefox is generally the browser that works best with the site, though if you're using a very old version (anything before about 1.5) you might wish to upgrade it to something more recent. Can you describe the problem you're seeing in more detail?
Do you press the reply link and then not get a reply field? Or get the reply field but are unable to submit?
-- Jacquilynne, Community Manager for Chowhound