ASP.NET file extensions

*aspx-ASPX is a text file format used to create Webform pages; in programming jargon, the ASPX file typically contains static HTML or XHTML markup, as well as markup defining Web Controls and Web User Controls where the developer places all the required static and dynamic content for the web page.
* asax - Global.asax, used for application-level logic and event handling[1]
* ascx - Web UserControls: custom controls to be placed onto web pages.
* ashx - custom HTTP handlers
* asmx - web service pages.
* axd - when enabled in web.config requesting trace.axd outputs application-level tracing. Also used for the special webresource axd handler which allows control/component developers to package a component/control complete with images, script, css etc. for deployment in a single file (an 'assembly')
* browser - browser capabilities files stored in XML format; introduced in version 3.0. ASP.NET 2 includes many of these by default, to support common web browsers. These specify which browsers have which capabilities, so that ASP.NET 2 can automatically customize and optimize its output accordingly. Special .browser files are available for free download to handle, for instance, the W3C Validator, so that it properly shows standards-compliant pages as being standards-compliant. Replaces the harder-to-use BrowserCaps section that was in machine.config and could be overridden in web.config in ASP.NET 1.x.
* config - web.config is the only file in a specific Web application to use this extension by default (machine.config similarly affects the entire Web server and all applications on it), however ASP.NET provides facilities to create and consume other config files. These are stored in XML format, so as to allow configuration changes to be made with simplicity.
* cs/vb - In ASP.NET 2 any cs/vb files placed inside the App_Code folder are dynamically compiled and available to the whole application.
* master - Master Pages; introduced in version 2.0
* sitemap - sitemap configuration files
* skin - theme skin files.
* resx - resource files for internationalization and localization. Resource files can be global (for e.g. messages) or "local" which means specific for a single aspx or ascx file.