Deb Harrison

He's probably referring to the fact that html emails have to be coded in a very old-fashioned way - no stylesheets, no head section style tags, use old-style tables, repeat styles in every td cell, use absolute urls for images, no background images (Outlook 2007/2010 doesn't process them), etc.
 
Here are some of the coding issues that I have found important:-
 
Use tables preferably with old-fashioned styles like bgcolor="#eeeeee" instead of CSS inline styling like style="background: #eeeeee;" if there is a choice, otherwise use inline styles, as some email systems seem to process the old table styles better than inline CSS.
Don't use an external stylesheet or head section style tags.
Use absolute urls like http://www.your-domain.com/images/photo.jpg instead of relative urls like images/photo.jpg for images and include width="600" height="193" alt="Image description".
I found that if I looked at an html email that had been addressed to a hotmail address using Firefox to view it as webmail the code style="font-family: serif;" was ignored and it showed as a default Arial font style while IE, Outlook, AOL and other smtp email programs showed serif. Using the old format font family="serif" made no difference (font face is deprecated). I made Firefox show serif by coding style="font-family: Times, serif;".
Don't put styles in the table tag unless they relate only to the table envelope; repeat styles for every <td> tag like
<td style="font-family: Times, serif; font-size: 16px; color: #ff4500; font-weight: bold; border: none;">......</td>
Don't use general styles like style="border: 2px solid #ddd333;" but show each separately like border-top: 2px solid #ddd333; border-right: 2px solid #ddd333;" etc., etc.
If you want to show a background image, note that Outlook 2007 does not show background images although Outlook 2002 does. Other email programs have difficulties with background images unless they are coded in a certain way. Hotmail will not show a background image if it's coded for a whole table which has more than one <td>...</td> tag, so the method to use is to set up an outer table which only has one row and one <td>...</td> tag with <td style="background-repeat: no-repeat; background-color: #ffffff;" background="http://www.your-domain.com/images/photo.jpg"'>http://www.your-domain.com/images/photo.jpg" width="600" height="488" valign="top"> for the <td> tag and put the table which has several <td>...</td> tags inside. The width and height are whatever you want for the email, preferably the width of the background image and the height will increase automatically if it's needed for more content in the nested table, and the background-repeat: no-repeat inline style should stop the image repeating in email systems that process inline styles.
Most email programs edit your html code, stripping out some items and adding others. If you send an html email to a hotmail address and then forward it back to yourself you can look at the source code to see what Hotmail has edited. For instance, <td style="margin: 5px; border-bottom: #aaaaaa 5px solid; border-left: #aaaaaa 5px solid; border-top: #aaaaaa 5px solid; border-right: #aaaaaa 5px solid; background-repeat: no-repeat; background-color: #ffffff;" background="http://www.your-domain.com/images/photo.jpg" width="600" height="488" valign="top"> becomes <TD style="BORDER-RIGHT: #aaaaaa 5px solid; BORDER-TOP: #aaaaaa 5px solid; BORDER-LEFT: #aaaaaa 5px solid; BORDER-BOTTOM: #aaaaaa 5px solid; BACKGROUND-REPEAT: no-repeat; BACKGROUND-COLOR: #ffffff" vAlign=top width=600 background=http://www.your-domain.com/images/photo.jpg height=488>. Note that Hotmail has deleted the margin as it doesn't process margin. Color is often replaced with RGB(170, 170, 170) code.

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