CSS display inputs in-line (last input width:100%)

With a little CSS you can do this. Wrap the last input in a span and add this CSS:

<div style="width:300px;background:#eee;height:30px;">
    <input value="first" style="width:80px" type="button"/>
    <input value="second" style="width:80px" type="button"/>
    <span id="last"><input value="last" style="width:100%" type="button" /></span>
</div>
#last {
    overflow:auto;
    display:block;
}
input {
    float:left;
}

jsFiddle example