Remove portal page margin-bottom from body

[Joe B2]

I'm rebuiding our login page and there appears to be a default margin of 3rem at the bottom of the page:

The page I'm setting up has a graphic in the background and the background colour, set to white in this instance, is an obvious stand out.

I'm having trouble affecting the css on this element and there are a number of styles affecting this element:

Using the browser developer tools to set the above items to 0rem does work but actually getting them to acknowledge a style change is eluding me.

I tried putting the following in the page CSS:

body{
   margin-bottom: 0px;
}

I have also put this in the column CSS and in the body of the primary widget on the page itself.

Seems like this should be straightforward so unsure what I am missing.

Has anyone managed to do this or know how I might proceed?

Thank you.

[Joe B2 · Accepted solution]

So this turns out to have been an obvious oversight on my part. I had assumed it was an inbuilt function, such as the default padding added to the top and left of containers on the portal builder.

Turns out it was just some custom CSS added into the portal's theme to always put a margin at the bottom of the body.

Putting this out there in case anyone else comes accross this and missed it like me.