Hi Mohammad,
No, I’m with the last 2.17 version. My cart page is fine.
The styling issue is at the thank you page and at the order details page (when looking at the order details from My Account).
The file at fault is order-details.php, where “Order Details” (line 41) and “Customer Details” (line 191) titles do not have the same h tag. It’s nothing more than that, probably just a typo.
As the css, I didn’t dig into that precisely but it looks like the theme style doesn’t apply to these headings. Firebug shows the following classes : .woocommerce-checkout .checkout-confirmation h2 or h4.
Thank you,
Ammie