[O] org-table: missing vertical boundary when exported

[Shiyuan]

Hi, 

    I am following the manual example http://orgmode.org/worg/org-tutorials/tables.html. But the two vertical boundary line on the very left and right 

is not showing up when exported to html.  Anything I am missing? Thanks. 

|   |  N | N^2 | N^3 | N^4 | sqrt(n) | sqrt[4](N) |

|---+----+-----+-----+-----+---------+------------|

| / | <> |   < |     |   > |       < |          > |

| # |  1 |   1 |   1 |   1 |       1 |          1 |

| # |  2 |   4 |   8 |  16 |  1.4142 |     1.1892 |

| # |  3 |   9 |  27 |  81 |  1.7321 |     1.3161 |

|---+----+-----+-----+-----+---------+------------|