inherit

There is one keyword that is shared by all properties in CSS2.1: inherit. inherit makes the value of a property the same as the value of its parent element. In most cases, you don't need to specify inheritance, since most properties inherit naturally; however, inherit can still be very useful.

For example, consider the following styles and markup:

Pixel in CSS

CSS2 recommended 90ppi as the reference pixel, but CSS2.1 recommends 96ppia measurement common to Windows machines and adopted by modern Macintosh browsers such as Safari. This means when I display 96 pixel in my screen, it should be 1 inch length in physics. But if my screen is about 110ppi, so 1 inch in css is going to less than 1 inch in my scree. But how about printer, it normally print 600ppi. It actually first convert pixel in screen to inch in scree, then print the length in inch in printer, and print the pixel by timing 600ppi to length in inch.

Unit in css

All length units can be expressed as either positive or negative numbers followed by a label (although some properties will accept only positive numbers). You can also use real numbersthat is, numbers with decimal fractions, such as 10.5 or 4.561. All length units are followed by a two-letter abbreviation that represents the actual unit of length being specified, such as in (inches) or pt (points). The only exception to this rule is a length of 0 (zero), which need not be followed by a unit.

Make IE more css2.1 compliant

Check here

Nullable and ?? Operator

After reading the article, The C# ?? null coalescing operator (and using it with LINQ), I did a quick test like the following code. It seems the compiler does different thing for Nullabe type, and other reference type with ?? operator. In fact, ?? should not be called operator, it is shortcut for compiler instruction. It will be more effective to use "t1.GetValueOfDefault()" than "t1 ?? 0" . But latter seems more language built-in feature than API.