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.