Force IE8 Into IE7 Compatiblity Mode

UPDATE January, 2017:

According to Can I use, the user-select is currently supported in all browsers except Internet Explorer 9 and its earlier versions (but sadly still needs a vendor prefix).

These are all of the available correct CSS variations:

.noselect {
  -webkit-touch-callout: none; /* iOS Safari */
    -webkit-user-select: none; /* Safari */
     -khtml-user-select: none; /* Konqueror HTML */
       -moz-user-select: none; /* Old versions of Firefox */
        -ms-user-select: none; /* Internet Explorer/Edge */
            user-select: none; /* Non-prefixed version, currently
                                  supported by Chrome, Edge, Opera and Firefox */
}

<p>
  Selectable text.
</p>
<p class="noselect">
  Unselectable text.
</p>

Note that user-select is in standardization process (currently in a W3C working draft). It is not guaranteed to work everywhere and there might be differences in implementation among browsers. Also, browsers can drop support for it in the future.

More information can be found in Mozilla Developer Network documentation.

The values of this attribute are none, text, toggle, element, elements, all and inherit.

Cross-browser @media (width) and @media (height) values 

const vw = Math.max(document.documentElement.clientWidth || 0, window.innerWidth || 0)
const vh = Math.max(document.documentElement.clientHeight || 0, window.innerHeight || 0)

window.innerWidth and window.innerHeight

• gets CSS viewport @media (width) and @media (height) which include scrollbars
• initial-scale and zoom variations may cause mobile values to wrongly scale down to what PPK calls the visual viewport and be smaller than the @media values
• zoom may cause values to be 1px off due to native rounding
• undefined in IE8-

document.documentElement.clientWidth and .clientHeight

• equals CSS viewport width minus scrollbar width
• matches @media (width) and @media (height) when there is no scrollbar
• same as jQuery(window).width() which jQuery calls the browser viewport
• available cross-browser
• inaccurate if doctype is missing

Resources

• Live outputs for various dimensions
• verge uses cross-browser viewport techniques
• actual uses matchMedia to obtain precise dimensions in any unit