wordpress / css – what is the code for a “return” key press

So as most developers, i use a CSS RESET in all my work. One of the small problems i run into is that when developing custom anything in wordpress, i use this reset and the problem ive been having is that, because of said reset when the user is writing a post, the ability to for example, use italics / bold etc isnt available. I mean it is but its not applied because of said reset.

I just went in and removed the em / i / b etc tags from the reset block and its working BUT, theres one more thats giving me the biggest problem and thats that when someone hits the enter key to create space between text etc, nothing happens. they have to manually go in and put in <br/> tags to create the separation.

That said, it got me to thinking that….what exactly IS the css for line breaks/ the enter key?

below is whats in my CSS reset…not sure what else i have to remove.

html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn,  img, ins, kbd, q, s, samp,
small, strike, sub, sup, tt, var, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed, 
figure, figcaption, footer, header, hgroup, 
menu, nav, output, ruby, section, summary,
time, mark, audio, video {
    margin: 0px;
    padding: 0;
    border: 0;
    font-size: 100%;
    font: inherit;
    vertical-align: baseline;
}
/* HTML5 display-role reset for older browsers */
article, aside, details, figcaption, figure, 
footer, header, hgroup, menu, nav, section {
    display: block;
}
body {
    line-height: 1;
}
ol, ul {
    list-style: none;
}
blockquote, q {
    quotes: none;
}
blockquote:before, blockquote:after,
q:before, q:after {
    content: '';
    content: none;
}
table {
    border-collapse: collapse;
    border-spacing: 0;
}

a{text-decoration:none;}

Ive tried to google but, aside from the p tag or the div tag etc…not sure what i have to remove to get the enter key/space created by pressing the enter key to go back to default.

Thanks in advanced.