Border of cell in HTML lost.

```
What steps will reproduce the problem?
1.add thin border at example.xls cell(30,C).

What is the expected output? What do you see instead?
The result should be whole cell rounded by thin black border in HTML. But
the result is just right and bottom border added and left and top missing.

Please provide any additional information below.
This also happen on merged cell. It is very unstable when handling border
of cells.

Any one can help to improve this?
```

Original issue reported on code.google.com by `andes...@gmail.com` on 24 May 2010 at 4:22

Reproduce the issue with example.xls using cell (30,C), then inspect the HTML export handling for regular and merged cells. Done means the generated HTML shows a complete thin black border on all four sides of the cell, including merged cells.

Written by the indexing model from the issue text.