Какие теги HTML вы бы использовали для описания таблицы следующим образом:
+--------+---------+---------+---------+
| TH1 | TH2 | TH3 | TH4 |
+--------+--------+---------+---------+---------+
| TR1 | str1 | 1 | 1 | 1 |
+--------+--------+---------+---------+---------+
| TR2 | str2 | 1 | 2 | 1 |
+--------+--------+---------+---------+---------+
| TR3 | str3 | 1 | 1 | 3 |
+========+========+=========+=========+=========+
| total | 3 | 4 | 5 |
+--------+---------+---------+---------+
И второй:
+--------+---------+---------+---------+
| TH1 | TH2 | TH3 | TH4 |
+========+========+=========+=========+=========+
| GROUP 1 |
+--------+--------+---------+---------+---------+
| TR1 | str1 | 1 | 1 | 1 |
+--------+--------+---------+---------+---------+
| TR2 | str2 | 1 | 1 | 1 |
+========+========+=========+=========+=========+
| GROUP 2 |
+--------+--------+---------+---------+---------+
| TR3 | str3 | 1 | 1 | 1 |
+--------+--------+---------+---------+---------+
| TR4 | str4 | 1 | 2 | 1 |
+--------+--------+---------+---------+---------+
| TR5 | str5 | 1 | 1 | 3 |
+========+========+=========+=========+=========+
| total | 5 | 6 | 7 |
+--------+---------+---------+---------+
(при условии высокого уровня доступности)