Header border is bold

[thuythao1912]

Question I'm want to make the bottom border of header thinner (image 2). The current status is image 1. Could you help me?

(image 1)

image 2

my code

I'm looking forward for your support. Thank you all!

[Ymbere]

Hi, @thuythao1912 I think that you are having some issues with your CSS, you can look at the example below, I think that's the way you want the header of your table.