Table nested 3 levels, table3 be the out most.
Table 1 is not in table2's tr-td. That makes table2 invalid.
Table3 is still valid, and table2's tr and td are used for table3.

caption of table3.
caption of table2.
Text after table2, not in tr-td, but in table3's tr-td.

caption of table1.
first cell in table1 | second cell in table1
third cell in the table1 | fourth cell in the table1

first cell in table2, but displayed in table 3.
| second cell in table3. but table2's end tag closed table3. So, this will be displayed out of table3.