line break tags in posts

i just installed wordpress on two of my sites, and i’ve noticed that when i put <br /> tags into my posts, they don’t seem to appear on my site. when i go to edit, they’re there, but between publishing and viewing, they seem to disappear. i try doing many of them, but that doesn’t work. i’ve also tried <p></p>, but that also doesn’t work. am i supposed to do something? i’m using the non-visual rich editor, if that matters.