I'm researching building a site by looking at what other people have done but I don't know how to determine what technologies or platforms are being used. How can I tell what any given site is running when I visit it?
There are four basic things you can check to determine what any given site is running:
Server. Checking to see what web server a site runs can also help give you clues as to how it was built. Sometimes this is pretty easy to figure out...if you see a file extension of .cfm or .asp/.aspx then you are on pretty solid ground with knowing which technologies are in play. If a site uses permalinks or other method to obfuscate the extension, check it against Netcraft to get a report of what server it is running on or you can use some tricks like issuing a telnet to servername on port 80 or a curl command to see the response header and that will tell you what the server environment is like. Combining what you learn in these two steps with experience and some extra Googles will usually tell you what you want to know.
http://example.org/humans.txtto see if developers already listed everything for you.
Check the headers of a page with a console/debugtool. You might find info like
X-Powered-By PHP/5.3. This site is build with PHP on an Apache server.
Ask. Believe it or not, people may just tell you.
There are also browser plugins and other tools that will analyze a site and show you what is running. One of the more popular examples of this is Wappalyzer which has extensions for both Firefox and Chrome and is worth a look for you.
You can get a breakdown of what different components a site uses using Built With.
When a site uses a content management system such as Wordpress, it usually shows up there. In the case of the site you are asking about, it does not show a content management system but the following libraries: jQuery, FancyBox, JQuery Mousewheel plus a number of widgets.
1.I get the http headers, sometimes it tells you something (for instance if it is ran by php).
2.I can type mywebsite.com/wp-login.php, if a login page appears it means the website uses wordpress.
3.If a login page appears by typing mywebsite.com/admin it means it uses drupal.
4.If a login page appears by typing mywebsite.com/administrator it means it uses joomla.
See this question over on Stack Overflow for a pretty complete answer