There are two types of
numbers in CSS: integers
("whole" numbers) and
reals (fractional numbers).
These number types serve primarily as the basis for other value
types, but, in a few instances, raw numbers can be used as a value
for a property.
In CSS2.1, a real number is
defined to be an integer that is optionally followed by a decimal and
fractional numbers. Therefore, the following are all valid number
values: 15.5, -270.00004, and 5. Both integers and reals may be
either positive or negative, although properties can (and often do)
restrict the range of numbers they will accept.
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