[html] HTML CSS Button Positioning

I have 4 buttons in a header div. I have placed them all using margins top and left in css so they are all next to each other in one line. Nothing fancy.

Now I'm trying to do an action when the button is pressed the button text moves down a little bit.

I'm using this code in CSS :

    #btnhome:active{
    line-height : 25px;
}

HTML :

<div id="header">           
        <button id="btnhome">Home</button>          
        <button id="btnabout">About</button>
        <button id="btncontact">Contact</button>
        <button id="btnsup">Help Us</button>           
        </div>

Button CSS example :

#btnhome {  
    margin-left: 121px;
    margin-top: 1px;
    width: 84px;
    height: 45px;   
    background: transparent;
    border: none;
    color: white;   
    font-size:14px;
    font-weight:700;
}

Also those buttons work on a header background, I'm sure it has something to do with these settings :

#header {
    background-image: url(images/navbar588.png);
    height: 48px;
    width: 588px;
    margin: 2em auto;   
    }

It works well but the only problem is that the all other buttons also move their text down? Why Is that? Aren't I clearly clarifying that I want to use #btnhome only? All the buttons have completely different ID's. All buttons have the same CSS settings except the margins. What do I need to edit?

Thank you very much.

Use margins instead of line-height and then apply float to the buttons. By default they are displaying as inline-block, so when one is pushed down the hole line is pushed down with him. Float fixes this:

#header button {
    float:left;
}

Here's a working jsfidle.

[type=submit]{
    margin-left: 121px;
    margin-top: 19px;
    width: 84px;
    height: 40px;   
    font-size:14px;
    font-weight:700;
}

try changing that line-height change to a margin-top or padding-top change instead

#btnhome:active{
margin-top : 25px;
}

Edit: You could also try adding a span inside the button

<div id="header">           
    <button id="btnhome"><span>Home</span></button>          
    <button id="btnabout">About</button>
    <button id="btncontact">Contact</button>
    <button id="btnsup">Help Us</button>           
</div>

Then style that

#btnhome span:active { padding-top:25px;}