xml file styling when opening in Excel 2010

Question

How to make columns center or assign columns as string/integer/decimal when you open an xml file with excel 2010.  or a font?

Here's an example of the xml file:

<?xml version="1.0"?>
<RecycleBin>
  <Site Url="https://www.site.com" Size="16489369" />
</RecycleBin>

So I've read some blogs about different ways to do this.. when you open the xml file it asks you if you want to use a schema..

The different ways I've seen are a variety .. including something called DTD, CSS, Schema, xsl. 

So what is currently the best practice.. This is for .net 3.5 ... possibly an example?