Question

If I have container and I floated it to the right, will elements I float inside(eg. left) float to the left until it reaches edge of float container? Or I need to assign position:relative; for float to control it inside container?

Answer 1

It will float wherever you want it to float.
Take a look http://jsfiddle.net/79nRM/:

HTML

<div class="placeholder">
    <div id="container">
        <div class="element left"></div>
        <div class="element right"></div>
        <div class="element left"></div>
        <div class="element right"></div>
        <div class="element left"></div>
        <div class="element right"></div>
    </div>
</div>

CSS

.placeholder {width:400px; height:400px;background-color:#cecece;}
#container {float:right;width:200px;height:400px;background-color: Blue;}
.element {width:50px; height:50px;background-color: Red;clear:both;}

.left {float:left;}
.right {float:right;}