Not able to center Input elements in Div - html

Question

I have tried googling but with no help most of them give solution as margin:auto
and also there are several questions on stackoverflow with same problem most of them have answer as margin:auto i am applying the same solution is not working for me
HTML
<div id="content" class="lcard">
<center>
<h1 class="n">Sign in To your<br> Crawler Account</h1><br>
<form onsubmit="return validateForm()" method="post">
<center><input name="Email" required type="email" placeholder="Email">
<input name="Password" required type="Password" placeholder="Password" >
<button type="submit" class="b"><b>Sign In</b></button>
</center>
<p id="reg" ><a href="C:/lcrawl/register.html" >New User Please Register</a></p>
</form>
</div>
CSS
.lcard
{
background-color:#EEEEEE;
height:400px;
width:400px;
margin:left;
}
.n
{
margin-bottom:50;
left:-50%;
}
input
{
padding: 5 10px;
width:274px;
height:44px;
margin:auto;
}
.b
{
border: 1px solid;
background-color:#3079ed;
width:274px;
height:44px;
margin:auto;
}

Answer 1

Why you are giving margin left here??
.lcard
{
background-color:#EEEEEE;
height:400px;
width:400px;
margin:left;
}

Answer 2

First thing I noticed is the margin: left which I'm not sure about if it's a real value or not.
You should also check the attributes within your input elements. Types and other values seem strange, try to mess around with them first and then try using input[type="text"] and input[type="submit"] in the CSS values, instead of just **input.

Answer 3

Put your center tag before the first div as you call the id content
<div id="content" class="lcard">
<center>
<h1 class="n">Sign in To your<br> Crawler Account</h1><br>
<form onsubmit="return validateForm()" method="post">
<center><input name="Email" required type="email" placeholder="Email">
<input name="Password" required type="Password" placeholder="Password" >
<button type="submit" class="b"><b>Sign In</b></button>
</center>
<p id="reg" ><a href="C:/lcrawl/register.html" >New User Please Register</a></p>
</form>
</div>
should be...
<center>
<div id="content" class="lcard">
<h1 class="n">Sign in To your<br> Crawler Account</h1><br>
<form onsubmit="return validateForm()" method="post">
<center><input name="Email" required type="email" placeholder="Email">
<input name="Password" required type="Password" placeholder="Password" >
<button type="submit" class="b"><b>Sign In</b></button>
<p id="reg" ><a href="C:/lcrawl/register.html" >New User Please Register</a></p>
</form>
</div>
</center>

Answer 4

First, remove OLD OLD center blocks, than just apply text-align: center to form and to header. JSFiddle
.n
{
text-align: center;
}

Answer 5

I changed ur css a little
.lcard
{
background-color:#EEEEEE;
height:400px;
width:400px;
margin-left: auto;
margin-right: auto;
}
Now It's work in my PC.

Answer 6

Nothing's wrong with your code
Here is jsfiddle, with your code plus minor modification
http://jsfiddle.net/Lb6mm/2/