If you have an online course about React, Angular, CSS, good ol'plain CSS, whatever. I made a checklist you can use to review your own course sales page

Be Unique with a Unique Headline

[ ] It's clear. If they read only the headline, they'll understand what's this course about
[ ] There's a differentiation between you and other teachers

The Teacher Story

[ ] I'm telling users who I am
[ ] I'm telling users why I decided to teach this course
[ ] I mentioned proof of success in my teacher story

Make them trust you

[ ] Does the fold include social proof (testimonials, companies you worked with, accomplishments)
[ ] Is there a repetition of social proof on the page
[ ] The social proof is relevant to the audience (if it's a freelancer Bootcamp, mention some testimonials from agencies freelancers )

Calm their anxiety

[ ] I know what makes my users fearful, uncertain, and doubtful of enrolling
[ ] I'm addressing the issues on your sales page

There's something for you, user!

[ ] I have an incentive (Money-back guarantee, discount, free e-book/manual/T-shirt, etc)
[ ] The incentive is clear in my copy and design
Are you offering value for people who won't buy
[ ] Almost everyone won't buy from the first time, are you giving them something to capture their emails?

My website looks aesthetically good

[ ] I've shown 20 people my website for only 5 seconds. They had a positive first impression

My website is easy to use

[ ] The most important things come first in the page
[ ] The most important things are more visible than the other elements (font weight, font size, color, position)
[ ] The contrast between foreground and background is OK
[ ] Consistency
[ ] Same colors
[ ] Same fonts
[ ] Consistent spacing
[ ] The images are relevant to the copy