Server error logs is not in the Admin CP. You need to check your cPanel or whatever script your web host uses.
thanks 2 all. i try to solve my problem, i think i cant find my answer.
^ well, it appears that captcha_fonts directory is missing on your site !!
That shouldn't be an issue, but just in case, download the attachment below, extract it and upload it to your /inc/ directory.
[
attachment=23176]