Hi 007JamesBond8, welcome to the forums!
Can you provide more details? What version of XD are you using? When you use the centering option the page is centered in the browser. If the page is smaller than the available browser width or height there is space on the sides.
The new version of Web Export there is a new
Scale to width option. This will scale the artboard up or down to fit all available space.
Here’s a preview:
To remove the margin on the sides:
- turn off
- turn on
Enable scale upwith
Scale to width