a, "1, Color Expression method summary: 1, English command color in front of a few sections of the often used is this setting method: p{color:red;} 2. RGB color This is consistent with the RGB color in Photoshop and is color-matched by the ratio of R (red), G (green), B (blue) three Colors. P{color:rgb (133,45,200);} The value of each item can be an integer between 0~255, or it can be a percentage of 0%~100%. Such as: P{color:rgb (20%,33%,25%);} 3, hex Color This color setting method is now more commonly used method, and its principle is actually RGB settings, but its value of each item from 0-255 to hexadecimal 00-ff. P{color: #00ffff;} "2, unit and value 1, pixel pixel why is relative unit?" Because pixels refer to dots on the display (the CSS specification assumes "90 pixels = 1 inches"). The reality is that the browser uses the actual pixel value of the display, and most designers now tend to use pixels (px) as Units. 2, em is the font-size value of this element given the font, if the element font-size is 14px, then 1em = 14px; If the font-size is 18px, then 1em = 18px. The following code: p{font-size:12px;text-indent:2em;} The code above is the ability to indent the first line of a paragraph by 24px (that is, The distance of two font sizes). Here's a special case: but when Font-size is set to em, the criteria for calculation are based on the font-size of the parent element of P. The following code:html:<p> the example of this <span> example </span>. </p>css:p{font-size:14px}span{font-size:0.8em;} As a result, the font "example" font size in span is 11.2px (0.8 = 11.2px). 3, percent p{font-size:12px;line-height:130%} Set the line height (line Spacing) to the 130% of the font (* 1.3 = 15.6px).
CSS Learning V-unit and value
