Použij tabulku a máš po problémech.
<table style="width: 80%; border-collapse: collapse;" align="center">
<tr>
<td><img src="foto 1.jpg" title="obr" alt="foto 1.jpg, 1,9MB" title="foto 1" height="300" width="400"></td>
<td><img src="foto 1.jpg" title="obr" alt="foto 1.jpg, 1,9MB" title="foto 1" height="300" width="400"></td>
<td><img src="foto 1.jpg" title="obr" alt="foto 1.jpg, 1,9MB" title="foto 1" height="300" width="400"></td>
</tr>
<tr style="text-align: center">
<td>Popisek 1</td>
<td>Popisek 2</td>
<td>Popisek 3</td>
</tr>
</table>