Sometimes mod_negotiation fails to select right veriant. At once after restart
it works, but after several page reloads it get 406 Not Acceptaple. This hapens
if, for exaple, browse send following headers

Accept:text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,video/x-mng,image/png,image/jpeg,image/gif;q=0.2,text/css,*/*;q=0.1
Accept-Charset: KOI8-R, utf-8;q=0.66, *;q=0.66
Accept-Language: ru, en;q=0.66, fr;q=0.33

After server restart atof at line 392 of mod_negotiation.c:
 result->quality = (float)atof(cp);
works right

text/html Quality: 0.9 -> 0.900000
text/plain Quality: 0.8 -> 0.800000
image/gif Quality: 0.2 -> 0.200000
*/* Quality: 0.1 -> 0.100000
compress Quality: 0.9 -> 0.900000
en Quality: 0.66 -> 0.660000
fr Quality: 0.33 -> 0.330000
utf-8 Quality: 0.66 -> 0.660000
* Quality: 0.66 -> 0.660000

(value before '->' is string passed as argument for atof function, value after -
is a value returned by atof)

Buf after i get 406 (Not Acceptable) it look like
text/html Quality: 0.9 -> 0,000000
text/plain Quality: 0.8 -> 0,000000
image/gif Quality: 0.2 -> 0,000000
*/* Quality: 0.1 -> 0,000000
compress Quality: 0.9 -> 0,000000
en Quality: 0.66 -> 0,000000
fr Quality: 0.33 -> 0,000000
utf-8 Quality: 0.66 -> 0,000000
* Quality: 0.66 -> 0,000000

If i change atof call at line 392 for this function:

static float ap_atoq(const char *str) {
  float result1 = atof(str);
  float result2 = 0.0;
  char *p = strchr(str, '.'), *d;
  
  if (p != NULL) {
    *p = ',';
    result2 = atof(str);
  } else {
    d = strchr(str, ',');
    if (d != NULL) {
      *d = '.';
      result2 = atof(str);
    }
  }
  if (result2 > result1) return result2;
  return result1;
}

it seems all work fine.

Probably, httpd-2.0 is also affected.