make sure to check out 'how to reference an element'
we can modify an elements css style at run time too, once we have a reference to is
all of the possible css styles on a html element are available via a property of the reference
we get from 'querySelector'. so if our element is 'myElementInJS' then all of its styles are in
'myElementInJS.style'. each css value has its own property in style, like 'myElementInJS.style.backgroundColor'
notice that instead of dashes, the names of the css properties use capital letters to denote word
you can set those css values to any valid thing you could set them to in a stylesheet. remember to