How to center divs on page - css

Question

In this fiddle : http://jsfiddle.net/H4F8H/16/
I'm attempting to center two divs by wrapping an outer div and centering it :
<div style="margin-left:auto;margin-right:auto;">
But the divs are remaining left aligned. How can I center these divs on page ?
fiddle code :
HTML :
<div style="margin-left:auto;margin-right:auto;">
<div id="block">
<img height="50" style="max-width: 50px;background-position: top left;" src="http://socialmediababe.com/wp-content/uploads/2010/12/administrator.jpg" />
<div style="font-size:20px;font-weight:bold;">
Test
</div>
<div>
Google
</div>
</div>
<div id="block">
<img height="50" style="max-width: 50px;background-position: top left;" src="http://socialmediababe.com/wp-content/uploads/2010/12/administrator.jpg" />
<div style="font-size:20px;font-weight:bold;">
Test
</div>
<div>
Google
</div>
</div>
</div>
CSS :
*{
margin:0;
padding:0;
}
#block {
margin-right:100px;
border-width: 2px;
border-color: #4682B4;
background-color: WHITE;
width: 100px;
text-align: center;
line-height:30px;
padding:3px 0;
float:left;
}
img{
float:left;
}
#block:hover {
background-color: #C2DFFF ;
}

Answer 1

div is a block level element by default so it will take up 100% of horizontal space if you do not assign some width to it, so you need to assign some width to your container
<div style="margin-left:auto;margin-right:auto; width: 300px;">
Here, you can just set the width accordingly. Also avoid using inline CSS.
Your CSS is lil sloppy, for example margin-right:100px; is not required, also, you can use shorthand like
margin: 0 auto; = margin-left:auto; margin-right:auto;
Demo (Added a red border just to show the boundaries)
Note: You are floating your elements, so make sure you clear your floats either by using <div style="clear: both;"></div> which I've already done in the demo provided, else you can also use the snippet below to self clear the parent like
.clear:after {
display: table;
clear: both;
content: "";
}

Answer 2

A couple things I want to point out in this post:
You have set Id="block" in two different instances. Id's are meant to be unique. If you want a reusable identifier you should be using classes.
Inline styling should be avoided when possible. In this case there is no need to set inline styling on the parent div.
There is more then one way to center div's
I am going to leave this link here: http://thenewcode.com/723/Seven-Ways-of-Centering-With-CSS
This would be my solution:
html:
<div class="container">
<div class="block">
<span>Test</span>
</div>
<div class="block">
<span>Test 2</span>
</div>
</div>
css:
.container {
display: flex;
justify-content: center;
align-items: center;
}
.block {
display: flex;
background: grey;
width: 30%;
height: 200px;
border: 1px solid #777;
margin: 5px;
}

Answer 3

Give a width to that container.
#outerdiv{
margin-left:auto;margin-right:auto;
width:500px;
}

Answer 4

<div align="center">
<!-- -staff ->
</div>

Answer 5

margin:auto; doesn't work unless the width is specified...
<div style="margin:auto;width:100px;">
your content here. [Replace the width with your choice]
</div>

Answer 6

Giving width and margin auto will centralise the content in specified width.
<div style="margin-left:auto;margin-right:auto;width:400px;">//give variable width here..Normally 1000 to 1018..
<div id="block">
<img height="50" style="max-width: 50px;background-position: top left;" src="http://socialmediababe.com/wp-content/uploads/2010/12/administrator.jpg" />
<div style="font-size:20px;font-weight:bold;">
Test
</div>
<div>
Google
</div>
</div>
<div id="block">
<img height="50" style="max-width: 50px;background-position: top left;" src="http://socialmediababe.com/wp-content/uploads/2010/12/administrator.jpg" />
<div style="font-size:20px;font-weight:bold;">
Test
</div>
<div>
Google
</div>
</div>
</div>

Answer 7

Like this
DEMO
CSS
.container{
width:960px;
margin:0 auto;
text-align:center;
border:1px solid red;
}