Why is this Invalid, HTML Options

[nugnat]

I am coding an email blast for someone so I am doing everything in html but I keep getting a message that the <h7> attribute is invalid. Does anyone know how to fix this?
This is what the online validator says.
118 Error: <h7> is not recognized!; Warning: discarding unexpected <h7>
<h7 style="font-size: 12px; font-weight:100; font-family: Arial, Helvetica, Geneva; margin: 0px 0px 5px 0px;">



<td height="90%" align="center" valign="top" background="images/grad_01.jpg"
style="background-repeat: no-repeat;"><p><img src="images/col_split-1.jpg" width="27" height="501" alt=""></p></td>
<td height="90%" valign="top"background="images/grad_01.jpg"
style="background-repeat: no-repeat;"><p><img src="images/ter-cci_03.jpg" width="235" height="100" alt=""><br>

<h5 style="font-size: 18px; font-weight:100; line-height: 1; font-family: Arial, Helvetica, Geneva; color: #9dc49a; margin: 20px 0px 5px 0px;">
COURSE DATE & TIME</h5><br>

<h7 style="font-size: 12px; font-weight:100; font-family: Arial, Helvetica, Geneva; margin: 0px 0px 5px 0px;">
Saturday, January 30, 2016<br>
9:00am – 5:30pm</h7>
<br><br>

[pandy]

Because H7 doesn't exist. There are only headings 1 - 6. And they are elements, not attributes.

See http://htmlhelp.com/reference/html40/block/ .