I’m confused…I thought you were styling the GridHead H1 tag?
However, if you are now styling the div with a class of GridBody you can add this to your CSS
and delete the inline styling from the HTML.
Frankly, I would remove the inline styling anyway from the HTML first and see what it looks like without that styling.
Remember that this will affect ALL divs with a class of GridBody where there is no inline styling.
BUT….you may not need to add that CSS to your file.
You probably won’t need to set a width as it will default to 100%.
I don’t set heights for divs either as they will, generally, be as tall as they need to be to hold the content. If I need them to have a little room I would do that through padding in the CSS.