Stretched width div background image

I am creating HTML and CSS for a template that will be eventually made into a custom Wordpress theme: http://www.lucky-magpies.co.uk/esm/ and would like to know the best way to make the photographic background stretch to the full width of the user’s screen?

I have added the image reference in the HTML (as <div style=“background…”) because the image is going to be different on each page
of the site.

(I am aware the image i’m using currently is too low in resolution but wanted to get the coding right first).

Also, I would like to use fonts ‘bebas’ and ‘aller’ any advice on the best way to embed these so they work in Wordpress.

Any help is very much appriciated.