A common question when starting in web design is, "should I use Linux hosting or Microsoft hosting?"
If you don't already have a preference, I recommend using Linux-based hosting. (For example, Site5 Web hosting.)
Linux hosting, and in particular the Apache server, is the most common setup that you will encounter when working on web sites, especially when starting out. The configuration is often referred to as LAMP, which stands for Linux, Apache, MySQL, and PHP. The "P" also sometimes refers to Perl or Python.
The huge user base, and open-source philosophy behind LAMP technologies means that there are countless tutorials, forums, newsgroups, IRC channels, user groups, and other online and offline resources for obtaining assistance with any server issues that you might encounter.
Linux servers allow you to SSH into them and perform useful administrative tasks from the terminal as if you were on your own local computer.
There are other excellent UNIX-based hosting options like BSD, but they are less common than Linux hosting. Linux is the best choice when starting out because it is so common and there is so much information and help available.
I strongly prefer Apache servers to Microsoft IIS servers. When using Apache servers, you have far more options for search engine friendly open source PHP/MySQL content management systems like Drupal and WordPress. There are also many other non-PHP/MySQL-based open source content management systems available. Some of those open source content management systems may work under IIS, but with reduced functionality or complicated workarounds because IIS doesn't use .htaccess files.
If you are just beginning with web design/development, I highly recommend learning PHP/MySQL over ASP.NET. I run across many more sites that were built in PHP than ones done with ASP or ASP.NET. As mentioned above, there are many open-source content management systems available that are written in PHP/MySQL. Learning PHP means that you don't have to start from scratch when building sites. You can take a system like WordPress or Drupal and customize it.
PHP/MySQL programmers are always in demand. Even large, heavily trafficked sites like Digg.com are powered by PHP and MySQL. Some familiarity with PHP and MySQL is very useful for doing web site maintenance and/or search engine optimization on sites that have been created by other people.
Linux servers are not limited to just PHP though. You can also choose from popular server-side scripting languages like Ruby, Python, and Perl, among others. These languages can often be found on Microsoft hosting plans, but when using open source code in your own projects on Microsoft hosting you may have to find a workaround for IIS' lack of .htaccess support.
ASP.NET, when used with VisualStudio, offers a WYSIWYG web development environment, but creating sites with WYSIWYG generally creates bad code. If you are interested in search engine friendly web sites, it is best to avoid WYSIWYG tools. Hand coding gives much more control. Microsoft's WYSIWYG editors make especially bad code that often (conveniently for Microsoft) is limited to only running well in Internet Explorer.
Some people choose Microsoft products because they are more familiar with Microsoft's brand name than with the word "Linux". Goldman Sachs released a report about Linux called Fear the Penguin. Quoting the vnunet.com "Linux Set for World Domination" article:
With Windows remaining dominant at the low-end, including on the desktop, Goldman Sachs said that the largest opportunity for Linux is for "servers on which higher-end, mission critical enterprise applications and databases are run".
Mission-critical performance for your servers, at a cheaper rate than Microsoft servers.
Linux, and other Unix variants like BSD, power some of the largest sites on the Web, including Google, Yahoo (BSD, PHP, and Symfony), Amazon.com, and many others. Linux also powers the world's fastest supercomputers.
Linux hosting is not only better than Microsoft hosting (in my opinion), it's also usually cheaper in the long run. Microsoft's MS SQL is much more expensive than MySQL. If you need more than one database, or need to scale your web site, Linux hosting will probably be much cheaper in the long run.
For example, the hosting company that I use (Site5 hosting) often has specials between $5 and $8 per month and offers just about every feature I need, including PHP5, MySQL, Ruby on Rails, and much more. Site5 is able to handle many thousands of visitors per day without trouble.
If you are just starting out and are wondering whether to use Microsoft hosting or Linux hosting, definitely go with Linux hosting. Linux hosting is more flexible and less expensive than Microsoft hosting. Using a Linux hosting plan will allow you to easily use free open-source content management systems like Drupal and WordPress without complicated workarounds for search engine friendly URLs.