STYLING TABS

Hello,
yesterday you gave me this code for styling my tabs:

ul.tabs {
background-color: #FF0000; /* Change background color */
}

ul.tabs li {
border-left-color: #000000;
border-right-color: #000000;
}

ul.tabs li a {
color: #FFFFFF; /* Text Color */
}

ul.tabs li.active {
background-color: #00FF00; /* Current Tab background color */
}

ul.tabs li.active a {
color: #0000FF; /* Current Tab text color */
}

It works, but I’ve tried to change the text size and it’s been impossible, can you tell me the code for that? Is it possible to change the border and sixe colour in the whole box?. And also de text appears with some kind of shadow I can’t delete, can you help me with this?

Kind regards
Amparo