There is no JavaScript that is doing this that I will cite below with my page, but yes, CSS itself, I do not know what that is, I tried to solve 'without making a fuss', but it did not work:
See for yourself, click the login button, which is actually a link, and you will see that the other link next to the name "CREATE AN ACCOUNT" also moves. How to solve?
A example playable in JSFiddle.
Do not leave the two elements in the same DIV, separate them.
See how I got it:
<div class="content">
<img src="layout/img/logo_completa.png" alt="CCSHOP" title="CCSHOP - Passagens aéreas e muito mais...">
<div class="login">
<a href="#" class="btn-newacc">Criar uma conta</a>
</div>
<div class="login">
<a href="#" class="btn-login">Fazer Login</a>
</div>
</div>
Notice that I added one more DIV with the login class, but clicking on one or the other does not affect the two elements at the same time.