Removing CSS parameter in a child theme

Hey all,

I did a search but didn't find this answer specifically. Apologies in advance if I've missed it.

I'm using the Social theme (which rocks!) for a site and also using the oembed plugin to embed videos etc from other sites.

In the base.css file line 268 there's this:
.widget object, .widget embed, .widget param {
display:block !important;
float:left;
height:auto;
margin:0;
max-width:100%;
padding:0;
text-align:center;
}

For some reason, the "height:auto" parameter causes all youtube videos to be squashed in height. If I turn off this parameter with firebug, it autosizes the player correctly. My question is how to actually turn off a parameter in the child-style.css. I can manually change the value to something like "420px" in this stylesheet, but I'd rather not set a value. I'm not sure why "auto" isn't doing the trick in the first place. Anyway, any help would be greatly appreciated thanks!