Hi, Daniel!
Thank you very much for so quick answer!
I can give you URL of my site, but it is uselessly now. I talked about my new site, it isn't ready jet and stans on local computer now. I hope it will be over to middle of Marсh. I'm planning to change my old host server and move a new site to new one.
I continued my experiments with JoomlaComments settings and get positive results. So there is some difference with displaying in Internet Explorer and FireFox, but right border returned to its place. So, this problem is not urgent now.
So, may be you can say, how can I remove some input fields from comment form, that appears by adding new comment (e.g. "theme" and "e-mail") and decrease font size in combo-box?