I assume this is for email hence the outdated html?
If so then the problem is that your table is invalid because you don;t have the same number of cells in each row. If you want something to span cells then you need to use 'colspan'.
<table align="center" border="1" cellpadding="0" cellspacing="0" width="600">
<td colspan="2" bgcolor="#70bbd9"><img alt="" src="/sites/default/files/email_images/pose_notification_redesign_email_final_01.jpg" style="width: 600px; height: 283px;" /></td>
<td style="padding: 0px;"><img alt="" src="/sites/default/files/email_images/pose_notification_redesign_email_final_02.jpg" style="width: 355px; height: 294px;" /></td>
<td style="padding: 0px;"><p>Hi Nathaniel,</p></td>
<td colspan="2" bgcolor="#ee4c50">Row 3</td>
You will also need to add a width to the cell if you want it only to fit the image where you have two cells across.
Columns and rows must always match up so when you span a row or column you need rowspan or colspan accordingly.
If this is indeed for an email then you would be better off avoiding rowspan and colspan anyway and instead use nested tables (each row is a single table and then you can have more cells in each table as required. Of course it does make alignment a little difficult sometimes).
If this is not for an email then start again and write it properly:)