Part I: The ABCs of CSS in Java

Encoding QR Code JIS X 0510 in Java Part I: The ABCs of CSS

Inheritance is useful because you don t have to specify that <strong>, the child of <p>, should also be colored green, or have other characteristics of the parent element Inheritance is obviously a time-saver with elements such as lists that have many children All the children turn green at once because they inherit that color from their parent A few properties are not inherited, however, because it doesn t make sense in some cases For example, you don t want child elements to inherit the margins used by their parents A main purpose of margins is to distinguish parent text blocks from child blocks, so they should have different margins Likewise, borders, padding, and backgrounds are not inherited

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3

Getting serious about selectors Using multiple declarations Grasping grouping Employing attributes as selectors Building your first style sheet Getting specific about CSS

ow that you ve been exposed to the wonders of CSS, you re unlikely to continue to write this kind of HTML:

That s the kind of line you d have to write perhaps dozens of times in a Web site Say, for example, that you have a series of warnings throughout your Web site, each preceded by an H3 headline in red For each headline, you had to specify that it was red using the <font> element Along comes CSS Now you can create a single H3 selector in a single location, yet it affects all the H3 headlines throughout the entire Web site That one style makes all H3 headlines red automatically If you later decide to change H3 headlines from a red color to simply boldface, no problem You need to make that change only once in the style sheet rule instead of dozens of places to H3 elements scattered throughout the HTML code A selector specifies to which element in the HTML code a CSS style rule is applied For example, use the selector p if you want a rule applied to HTML paragraph <p> elements Or use the selector h1 to define a CSS rule that is applied to the H1 headline elements in the HTML code In other words, a CSS selector is just an HTML element with its < > symbols stripped off Here s an h1 selector (shown in boldface), within a CSS rule:

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This rule means that throughout the HTML code, every H1 element gets selected to have the color red applied to it Selectors tell CSS what HTML elements to target for the application of the CSS rule But there s more to selectors than you might have suspected Consider some of the additional ways you can use selectors They re more versatile than you might suppose

You might wonder if you can affect everything in a Web site not just certain tags, but all tags You bet You can use a * to create a universal selector that has a global effect Perhaps one day your boss comes in your boss who has absolutely no taste or sense of design and says: Look I think we should make our Web site stand out from the crowd, so let s make the whole thing boldface! How about that You mean all the headlines No, I mean everything from the little captions to the text to the biggest headlines Everything! What a great idea Why stop there you ask, failing to remember that sarcasm is usually lost on your boss Why not also make the entire background a bright plaid Hey, I think you ve got something there! he says, and goes back to his office to think up some other subtle ideas Well, he is the boss To make the whole enchilada boldface without the use of a universal selector, you d have to create a group of selectors like this:

body, p, table, h1, h2, h3, h4, h5, h6, {font-weight: bold;}

Actually, you d have to create an even larger group, grouping most of the tags in your HTML, such as th, td, pre, strong, em, and any others you ve used or might use in the future Not to worry Rather than building an enormous group selector, you can just use a universal selector and change the text of your entire Web site to bold to make the boss happy, like this:

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