How can I find out with which software a web page was written?
hotel.info is probably written using Visual Studio, considering that it is built on ASP.NET, based on the fact that its URLs end with .aspx. There is a whole lot of scattered JS and custom-written HTML, though.
And a reply to BloodPhilia's answer: hotel.info contains the following <meta> tags:
<meta http-equiv="content-type" content="text/html; charset=UTF-8" />
<meta http-equiv="content-language" content="en" />
<meta http-equiv="content-style-type" content="text/css" />
<meta name="description" content="You can use hotel.info to obtain even better hotel prices, around the world. Whether you want a spa hotel, a boutique hotel, a conference hotel or 5 star luxury, searching for hotels with the hotel.info hotel reservation service is simplicity itself. A total of 1,000,000 real hotel reviews supplied by guests will help you select the best accommodation option for your next business trip, city break, short break or conference." />
<meta name="keywords" content="Hotel, search, book, reserve, Reservation, Hotels, Room, hotel.info" />
<meta name="robots" content="index,follow,noodp,noydir" />
<meta http-equiv="X-UA-Compatible" content="IE-7" />
<meta name="verify-v1" content=""/>
This question came up on Stack Overflow a while back.
From that link, there is a tool called BuiltWith that determines many of the platforms/libraries the site is built on.
If you're talking about what server-side software was used to build the site, there's no definitive way to determine that; you really just have a few hints to go by. Here are a few:
Comments and meta tags might suggest something like "page generated by FrontPage", etc.
Some sites have their assets (CSS, JavaScript) references appended with long numbers like style.css?3893877834. This is common with Rails-developed sites, but others use that technique too.
The URL gives hints, like if you see .jsp, .php, .asp, aspx, .py (Python), .pl (Perl), etc., those are pretty dead giveaway as to the server-side language that was used. If you see .do in the URL or .action, it's probably Struts.
You can use sites like Netcraft to determine what web server (apache, nginx, IIS) is being used
Usually, in the source of the website, it's mentioned as a "Generator" meta-tag.
Wordpress for example, adds this to the source:
<meta name="generator" content="WordPress.com" />
Frontpage uses:
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">