How to keep the text in one line inside a table?

Simple, use nowrap tag.

Example:

<table>
	<tr>
		<td nowrap>Do not break this very loooooooooooooooooooooooooooooooooooooong sentence!</td>
	</tr>
</table>

Or:

<table>
	<tr>
		<td nowrap="nowrap">Do not break this very loooooooooooooooooooooooooooooooooooooong sentence!</td>
	</tr>
</table>