Счетчик средствами CSS, взамен мало кастомизируемого <ol>. From https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Counters

counters(args).css

/*Один счетчик поуровнево, разделитель второй аргумент*/
ol {
   counter-reset: item;
   list-style: none;
}
li {
   display: block;
}
li:before {
   counter-increment: item;
   content: counters(item, ".") " ";
}

/*это с определением стиля счета*/


li:before {
   counter-increment: item;
   content: counters(item, ".", lower-roman) " ";
}

counters.css

body {
  counter-reset: section;           /* Set the section counter to 0 */
}
h3:before {
  counter-increment: section;      /* Increment the section counter */
  content: "Section " counter(section) ": "; /* Display the counter */
}

css_counter+math.css

dl {
   counter-reset: term -1;
}
dt:before {
   counter-increment: term 3;
   content: counter(term) ". ";
}

two-counters.css

/*сквозная нумерация для второго уровня*/
dl {
   counter-reset: term definition;
}
dt:before {
   counter-increment: term;
   content: counter(term) ". ";
}
dd:before {
   counter-increment: definition;
   content: counter(term) "." counter(definition) " ";
}