Formatting HTML signature in Mail (Lion)
If your code is copied and pasted, the first thing I realize is the following:

&lt;span style="font-variant: small-caps;"&gt; &lt;font face="Arial" color="#404040"&gt; / Junior Software Engineer &lt;/font&gt; &lt;/span&gt; &lt;BR&gt;
    &lt;/td&gt;
&lt;tr&gt;
    &lt;td style="padding-left:5px;"&gt;


which means, the end tag

&lt;/tr&gt;


is missing. This might be the problem due to different renderings between mail and Safari.
It's worth a try.