Make ASP Textbox same width as Button width - asp.net

Question

I'm trying to make a log in form similar to Google Gmail where the email and password textboxes have exactly the same width but when I can't get it right especially with the button. Both have the same style yet the button appears shorter and has a margin-left.
ASP.Net Markup
<div class="loginWindow">
<asp:Login ID="Login1" runat="server" RenderOuterTable="False">
<LayoutTemplate>
<asp:TextBox ID="UserName" placeholder="Username" runat="server" CssClass="Logintextbox"></asp:TextBox>
<asp:RequiredFieldValidator ID="UserNameRequired" runat="server" ControlToValidate="UserName" ErrorMessage="User Name is required." ToolTip="User Name is required." ValidationGroup="Login1" ForeColor="White">*</asp:RequiredFieldValidator>
<asp:TextBox ID="Password" placeholder="Password" runat="server" TextMode="Password" CssClass="Logintextbox"></asp:TextBox>
<asp:RequiredFieldValidator ID="PasswordRequired" runat="server" ControlToValidate="Password" ErrorMessage="Password is required." ToolTip="Password is required." ValidationGroup="Login1" ForeColor="White">*</asp:RequiredFieldValidator>
<asp:Button ID="LoginButton" CssClass="Loginbutton" runat="server" CommandName="Login" Text="Log In" ValidationGroup="Login1" />
<asp:Literal ID="FailureText" runat="server" EnableViewState="False"></asp:Literal>
<asp:ValidationSummary ID="ValidationSummary1" CssClass="ValidationSummary" runat="server" ValidationGroup="Login1"></asp:ValidationSummary>
</LayoutTemplate>
</asp:Login>
</div>
CSS:
.loginWindow {
height: 340px;
width: 300px;
outline: 1px solid #e2e2e2;
border: none;
padding: 15px 25px 15px 25px;
margin: auto;
position: absolute;
top: 0;
left: 0;
bottom: 0;
right: 0;
overflow: auto;
}
.Logintextbox {
border: 1px solid #e2e2e2;
display: inline;
padding: 5px 10px 5px 10px;
margin:0;
width: 220px;
height:30px;
}
.Loginbutton {
border: 1px solid #e2e2e2;
display: inline;
padding: 5px 10px 5px 10px;
margin:0;
width: 220px;
height:30px;
}

Answer 1

try applying:
-moz-box-sizing: border-box;
-webkit-box-sizing: border-box;
box-sizing: border-box;
to all your elements. It makes it so the element's padding and border are added without causing an increase in overall width. inputs are usually rendered this way by default but there may be something different with the ASP rendered inputs. Try to rule this out at least.
http://css-tricks.com/box-sizing/
http://www.paulirish.com/2012/box-sizing-border-box-ftw/
check out the difference between box-sizing and non box-sizing
http://jsfiddle.net/Davidicus/f5r3R/