The Pattern & Practices group has released a new set of security guidelines. The WCF 3.5 Security Guidelines are for Web services created with Windows Communication Foundation (WCF) 3.5. They are based on principles where possible. The recommendations are also as contextual as possible, but abstracted for reuse. Use them as a starting point, but you will likely need to tailor for your scenario.

Centering a block of content is a common requirement when laying out a web page, but it's often not completely obvious how to do it. Here's a common way we do it, which has worked nicely for us:

For the HTML:

The "wrapper" is the container that the div you want to center will be inside of. The "block" is the div that contains your content.

<div id="wrapper">
<div id="block">
This div is centered inside it's parent div.<br/>
This div is centered inside it's parent div.<br/>
This div is centered inside it's parent div.<br/>
This div is centered inside it's parent div.<br/>
This div is centered inside it's parent div.<br/>
This div is centered inside it's parent div.<br/>
</div>
</div>

For the CSS:

Here's the styling for the wrapper and the block. Comments are included to help you understand how it works.

* { margin:0; padding: 0 } /* shortcut browser reset: optional */
#wrapper { 
text-align:center;        /* centers the #block */
padding:10px 0;           /* to separate the blocks a bit for this example*/
border:1px solid green;   /* to help you see the border */
}
#block { 
text-align:left;          /* removes the centering from #wrapper
width:250px;              /* width of your block
margin:0 auto;            /* 'auto' equalizes the left and right margins
border:1px solid red;     /* to help you see the border */
}

Here a screenshot of the results:

When creating user interface we rely on a common set of controls to solve common problems. Hopefully, the controls are common enough to use again and again and they provide a consistant interface for interaction with our web applications.  

A pattern describes an optimal solution to a common problem within a specific context.

From the IAWiki:

Patterns are optimal solutions to common problems. As common problems are tossed around a community and are resolved, common solutions often spontaneously emerge. Eventually, the best of these rise above the din and self-identify and become refined until they reach the status of a Design Pattern.

Each pattern has four primary components:

1. a title
2. a problem
3. a context
4. a solution

Yahoo! has created a common pattern library where they give visual examples of each pattern.