Hi maximus392,
I tested it and the test code is as follow:
<div style="width:200px;height:100px;border:1px solid blue;">HTML borders are best created with CSS.</div>
When I put the code to the HTML view and then switch to Normal view, the changes get reflected in the editor area.
We can also add border by clicking 'Box Formatting' button.
Please post your code here, we can have a test.
Regards,
Eric