InDesign is not an "e-pub editor". The current functionality is not to *create* an exact copy of your work as an e-pub, it's just there to *facilitate* to export existing content to a format to be worked on with a *real* e-pub editor.
To chnage table borders (and, indeed, do *anything* with regards to table formatting), you need to open the exported e-pub document and adjust the CSS style document, and optionally the HTML file. For most purposes, adjusting the CSS is enough. To edit the e-pub document, you can use a dedicated editor such as Sigil, or just manually unpack, edit, and re-pack the e-pub file. That is not straightforward, as it has a few demands, but it has been asked before and a quick Google query will show lots of ways to do so.
Um. (After re-reading :D) So yeah, you are on the right track there. Since table formatting does not carry over into the e-pub, you must change it manually.
Thx for reply. Now I know that I am on the right way. I am using Oxygen for edit. Sigil adds to much text to html code and some readers has problem to read epubs then.
But why developers did not add these two lines to html code is another question. Maybe in CS7... Ilja
I haven't followed this too closely, but if you just want to add one
line of CSS to your ePub export, just add a "custom CSS" file when
exporting from InDesign. InDesign CS6 (don't remember about previous
versions) has the option of attaching a custom CSS file to all your ePubs.