I am trying to set the width 100% on text box but it stretches out the container.. I have checked some questions of the similar kind but there seems no explanation as to why the problem happens.. I know to manually set the properties but I need to find out why this happens. and I am must do it using the 100% property value..

```
   <body>
     <form id="form1" runat="server">
        <div style="border:1px solid gray;">
            <input type="text" style="width: 100%;"  id="title"/>

        </div>

    <div>
    <a href="#" id="postfile" style="float:left;">Post</a><span style="display:none;  border:1px solid #ee1100; margin-left:10px; color:#cc1100" id="errormessage"></span>
    </div>

</form>

```