�۹���׳��:
em	�������r�鰪��The height of the element's font
ex	�r��x������The height of the letter "x"
px	����Pixels
%	�ʤ���Percentage


������׳��:
in	�^�oInches (1 �^�o = 2.54 ����)
cm	����Centimeters
mm	�@��Millimeters
pt	�IPoints (1�I = 1/72�^�o)
pc	�֥dPicas (1 �֥d = 12 �I)