Seems I found solution, may be it will help to somebody.
I disabled "development" & "extras-development" repositories, because I have this errors only if I'm using those repositories. Then I was trying other repositories in order to find latest firefox version. I tried dries, freshrpms, newrpms etc. But I had not found firefox > 1.0.7 there. Then I had asked google about "fedora 4 rpm firefox 1.5". First result was nrpms.net. I added their repository to my yum configuration, here is link: nrpms.net/Docs/Yum/nrpms.repo
Then I did "yum update firefox" and now I have firefox 18.104.22.168