Volatile Correction Model


Accessibility iconThis website has been designed to be accessible for the widest possible audience regardless of their ability. This includes making access as easy as possible for people with disabilities who may have special needs.

Choose from the following:

How the website caters for people with a disability

People with disabilities, such as a visual impairment, may use assistive technologies to use the Internet. Assistive technologies are products used by people with disabilities to help accomplish tasks that they cannot do easily otherwise.

Assistive technology comes in many different forms, some of these include:

  • text browsers (e.g. Lynx)
  • screen readers
  • speech synthesis (speech output)
  • alternative keyboards or switches
  • Braille
  • screen magnifiers
  • sound notification
  • speech recognition
  • voice browsers

Website optimised for Lynx Text Browser This website has been built so that people using the technologies listed above can access and use the information available.

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How to use the keyboard to navigate the website

Keyboard operation is required for users who are unable to use the mouse. For example, users with limited hand use may not have the fine motor control required to position the mouse pointer accurately on objects displayed on the screen. Blind users cannot position the mouse pointer because they can't see the screen.

The keyboard provides a precise, discrete method of navigating and selecting. Mobility impaired users using the keyboard can precisely navigate and select using the keyboard or assistive technology that emulates the keyboard.

  • Tab Index - the website has a tab index coded into each page to allow a sensible order for the keyboard navigation. This starts in the main content section and then moves through the navigation areas in the tab order.
  • Tab Key - use the 'Tab' key to move forward through the tab index on the page. To move backward hold 'Shift' and press the 'Tab' key. To activate a link when selected press the 'Enter' key.
  • Arrow / Cursor keys - for using radio buttons on a web page, select the first one with the tab key and then use the cursor / arrow up and down keys to move through the available radio buttons. To activate a link when selected press the 'Enter' key.
  • Space Bar - for using checkboxes on a web page, select the required checkboxes with the tab key and then use the 'space bar' to tick them. To activate a link when selected press the 'Enter' key.
  • Enter / Return key - To activate a link when selected press the 'Enter' or 'Return' key.

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How to use access keys on the website

We have provided a series of keyboard shortcuts intended to help users who have difficulty in using pointing devices such as a mouse. This web site uses the UK Government access key system and the following information summarises each of the keyboard shortcut commands available to you.

Depending on your browser type use one of the following:

Windows LogoWith Windows-based systems, in general, press the "Alt" key and the relevant access key:

  • Microsoft Internet Explorer version 6 or later » press "Alt" and the relevant number / letter, then press the "Enter" key
  • Mozilla Firefox version 2 or later » press "Alt" + "Shift" and the relevant number / letter at the same time
  • Netscape version 8.0 or later » press "Alt" and the relevant number / letter at the same time
  • Opera 8.0 or later » hold down the Shift key and press Escape, release both keys, then press the number of the accesskey

Mac LogoWith Macintosh-based systems, if you are using Safari, Camino or Mozilla Firefox press the "Crtl" key and the relevant access key.

Access keys used on this website
Alt + 1 Home page Links to the Home page
Alt + 2 Contact Links to the Contact page
Alt + 3 Accessibility Links to the Accessibility page (this page)
Alt + 4 Links Links to the Links page
Alt + 5 Site Map Links to the Site Map page

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How to change font size on your browser

If the text is too small to read you need to change your text size.

  • Internet Explorer 7
    select 'Text Size' from the Page menu and select the text size you want to use (default is medium)
  • Internet Explorer 6
    select 'Text Size' from the View menu and select the text size you want to use (default is medium)
  • Firefox 2+
    select 'Text Size' from the View menu and select either 'increase' or 'decrease'
    (reset with 'normal')

Look for similar functions in other browsers.

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How the website complies with web accessibility standards

All of these pages have been validated for level A of the W3C Web Content Accessibility Guidelines 1.0. As a result the pages will comply with the Disability Discrimination Act which ensures that websites are accessible to blind and disabled users.

Level A of the W3C Web Content Accessibility Guidelines 1.0 This website conforms to the Web Accessibility Initiative (WAI) level A.

For a full list of the checkpoints that we have addressed to reach this standard and make our web content accessible to people with disabilities, please see the guidelines area of the WAI website.

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How the website complies with the Disability Discrimination Act, 1995 (DDA)

The Disability Discrimination Act, 1995 (DDA) effectively places responsibility upon employers and suppliers of goods and services to provide reasonable adjustment and, more importantly, to remove any barriers that could result in discrimination.

Since 1999 the DDA has covered public facing websites and internal systems even giving examples in its Code of Practice such as: 'An airline company provides a flight reservation and booking service to the public on its website. This is a provision of a service and is subject to the Act'.

As this website has been developed with AA accessible code it effectively complies to the Disability Discrimination Act.

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How the website is built to work on all browsers

Website optimised for Internet Explorer and Mozilla Firefox This website is built using code compliant with World Wide Web Consortium (W3C) standards for XHTML 1.0 and CSS 2.0. The pages display correctly with currently available Internet browsers such as Internet Explorer, Mozilla Firefox and Safari on both Windows and Macintosh platforms.

The use of standard XHTML and CSS 2.0 code means that future versions of browsers will also display them correctly.

Valid XHTML 1.0 TransitionalXHTML stands for eXtensible Hyper Text Markup Language which is the language or coding used to write web pages. It contains information about the pages structure, appearance and contents.

Valid CSS 2.0Cascading Style Sheets (CSS) - CSS is a simple mechanism for adding style, for example fonts, colours and layout to web documents.

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How to print pages from this website

Printer icon The website has a specific CSS 2.0 stylesheet for printing. This means when you choose File - Print/Print Preview from your browsers menu the layout of the webpage will change to suit a printer. This will remove most of the images, background colours, menus and unecessary clutter from the screen so that the most important text areas of the page can be printed clearly. Check that the scale menu is set to Shrink to Fit so that none of the text is clipped by the page margins when printing.

If you wish to have an exact print of the website as it is displayed on screen please press the PrtScn button on the keyboard. This creates a screenshot of the website and places it in the computers clipboard memory. Then paste this into a program like MS Paint or MS Word using Ctrl & V on the keyboard.

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How to turn on Javascript in your browser

Javascript warning icon Many web pages, including some on this website, need you to switch on (or 'enable') Javascript. If you 'enable' Javascript in your browser, web designers can use additional tricks to resize the page or add extra functionality. For example drop down menus, buttons to make navigating websites easier and changing the cursor when you roll over an icon are all tricks done by Javascript.

Windows LogoWindows

  • Internet Explorer
  • Go to the Tools menu in IE and choose Internet Options.
  • Next click the Security tab.
  • Make sure the Internet Zone is highlighted and press the Custom Level button to open the security options.
  • Look for the entry near the bottom of the list which says Scripting, then Active Scripting and make sure it is enabled.
  • Press OK to close the panels. Now reload the page which needs Javascript.

Mac LogoMac

  • Safari
  • Go to the Safari menu or Edit menu and choose Preferences.
  • Click the Security tab.
  • You can check or uncheck Javascript here (Java settings are not for Javascript).
  • Close the panel. Now reload the page which needs Javascript.

Firefox logoFirefox (Windows/Mac)

  • Firefox users should go to the Tools menu and select Options.
  • Next click Content.
  • Check Enable Javascript (Java settings are not for Javascript) in the main panel, for more settings press Advanced.
  • Press OK to close the panel. Now reload the page which needs Javascript.

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Environment and Heritage Service The Scottish Government's Air Quality Management The Welsh Assembly Government Defra - Department for Environment, Food and Rural Affairs
This website is designed and hosted by King's College London, on behalf of the UK Department for Environment, Food & Rural Affairs and the Devolved Administrations.