What's one "small" UI/UX detail that makes a landing page feel instantly more professional?

Hey everyone,
As a front-end dev who focuses on landing pages, I'm always obsessed with the small details that build subconscious trust with a user.
It's easy to focus on the big things like the headline, but sometimes it's the small stuff that makes a page feel truly "premium" and trustworthy.
For me, a great example is custom, well-designed form validation. When you see a form that gives you instant, clear feedback as you type, it just feels like a more robust and professional product.
I'm curious to hear from other founders and devs: what's your favorite "small" UI/UX detail that makes you trust a landing page more?
Looking forward to hearing your thoughts!