https://www.codecademy.com/en/courses/web-beginner-en-f8mcL/1/2
Oops, try again. Did you add two table header cells within the row you just created within <thead></thead>? (Table header cells are <th></th>, not <td></td>!)
and i did what he said 
Please post a link to the exercise you are working on so that I can move your post the right category – or you should be able to do it yourself.
I was able to reproduce the error message by writing TD instead of TH, as instructed, and indicated by the error message.
This is the markup that raised the SCT error:
<thead>
<tr>
<td>Famous Monster</td>
<td>Birth Year</td>
</tr>
</thead>
If your code looks like this, then the problem is simple enough to fix. Change all the td's to th's.