When you use the CSS property border-collapse: collapse; on a table element, it will collapse all borders separating the table columns...
You can also achieve the same effect by setting cell-spacing and border spacing to 0 like this:
<table cellspacing="0" style="border-spacing: 0;">
If you prefer using CSS, you can do the following:
#table1 td {
font-size: 200px;
}
#table {
border-collapse: collapse;
border-spacing: 0;
}
<table id="table1" border="1" cellspacing="0">
<tr>
<td>1</td>
<td>2</td>
<td>3</td>
</tr>
<tr>
<td>1</td>
<td>2</td>
<td>3</td>
</tr>
<tr>
<td>1</td>
<td>2</td>
<td>3</td>
</tr>
</table>