If you've defined styles to div { ... } in your CSS, then you can't simply 'disable' them on a new div unless you explicitly redefine them to the default. If all you div styles are declared via class or id attributes, then using a bare div will have this same effect.
Example, bad CSS. This can't be overridden without explicitly giving your target div a class or id and redefining font-size.
div { font-size: 23em; }
Example, better CSS. If you define all your div CSS with classes and ID's then when you want default styling just use a unclassed, un-ID'ed div.
div.reallyBig { font-size: 23em; }
Without seeing your original markup its hard to be much more specific. You may need to reassign styles / classes / id's for your desired effect.