CSS help needed with margin

I am trying to integrate a script in my wordpress.

The installation and everything else have gone fine, the problem is now when i am trying to integrate it visibly.

When i add this to the css file the script work,

.left {
    float: left;
    margin: 0px 10px 0px 0px;
}

The problem is that the left code above also affects the menu bar and that is not good.

Is there anyway of putting something in front of the code i am trying to integrate to the left code above only affects the code i am trying to integrate?

The code looks like this and should be inserted just before the postmeta inside of single.php.

<?php $thumbsup->setup('Post: '.get_the_ID(), 'mini-thumbs')->render() ?>

I am hoping there is any CSS experts here.

Thanks in advance.