<td valign="top" width="75%" class="author-content">
<span style="float:left;margin:0px 7px 0px 0px;">
{$postrow[post].Picture}
</span>
or
<td valign="top" width="75%" class="author-content">
<span style="float:left; margin-right: 7px;">
{$postrow[post].Picture}
</span>