Disable CSS style?

We're using Rainbow Portal which automatically imports CSS files for the entire portal.  I've created a new .ASPX page and have it css styled exactly the way i want it within FF and IE using strict doctype.  However when portal's css information is applied to the page everything is a mess.  The portal's css is overriding base elements such as TD and TABLE and so my page is being drastically altered.  I've tried to add more specificty to my elements but for the most part this has been frustrating.

Unfortunately Im cant simply remove the portal's css file (it is required for a nav menu added to my page).  Is there a way i can disable all the portal css styles for a particular area within the body?  FOr instance I need to simply disable the settings on TD, TABLE, and TR so that it can take on my default properties within the page.

I';ve already tried using:
body, p, div,img, input, table,thead,tr,th,td,textarea,ol,ul
{
      font-family: inherit;
      padding:inherit;
      font-size: inherit;
      margin: inherit;
      background-color: inherit;
      border:inherit;
}      

but no luck.  Again I've tried to add more specificity and it has worked here and there but still many elements are taking on some other style.  If theres a simpler way to simply disable the offending portal css styles for an area i'd rather opt for that.

Thanks