CSS style=display:block not working

The problem with your style is the float: left, you have to clear the "floatness". At the p tag, include the clear:both, it tells the browser that nothing can float at its left or right.

<div class="abcd"  style="margin-left:10px;">
    <form id='some'>
        <fieldset style="display:block;float:left;">
            <input class="yy" id="sss" type="radio" name="group0" value="aaa"/> ABC

            <input class="yy" id="sss" type="radio" name="group0" value="aaa"/> ABC

            <input class="yy" id="sss" type="radio" name="group0" value="aaa"/> ABC

        </fieldset>
        <p style="clear:both">
            <input placeholder="Enter Name/Value" name="xxx" id="xxx" size="40" style="display:block;float:left;">
            <button type="button" id="xxx" style="width:100;">Process</button>
        </p>
    </form>
</div>

When using the float attribute you have to clear it so that other elements won't appear floating next to it. try adding clear: both to the css of the input box like this:

<input placeholder="Enter Name/Value" name="Name" id="NameID" size="40" 
style="clear:both; display:block;"/>