Popup html - 'td' or 'th' tags but not both?

[RandyMcGregor3]

I have created a very simple table with html in web map. The html has 'th' tags in the first rows and 'td' tags in subsequent rows, as shown below. When I paste it into the source code window in a text popup all the 'td' tags are converted to 'th'. I would like 'th' for the first row and 'td' for subsequent rows. HTML seems to insist on one or the other. Is this expected behavior? Thank you, Randy McGregor