flash interview questions(41-60)
Why call the subtended angle a “pixel”, instead of something else (e.g. “subangle”)?
In most cases, a CSS pixel will be equal to a device pixel. But, as you point out, the definition of a CSS pixel will sometimes be different. For example, on a laser printer, one CSS pixel can be equal to 3×3 device pixels to avoid printing illegibly small text and images. I don’t recall anyone ever proposing another name for it. Subangle? Personally, I think most people would prefer the pragmatic “px” to the non-intuitive “sa”.
Why was the decision made to make padding apply outside of the width of a ‘box’, rather than inside, which would seem to make more sense?
It makes sense in some situations, but not in others. For example, when a child element is set to width: 100%, I don’t think it should cover the padding of its parent. The box-sizing property in CSS3 addresses this issue. Ideally, the issue should have been addressed earlier, though.
How to use CSS to separate content and design ?
The idea here is that all sites contain two major parts, the content: all your articles, text and photos and the design: rounded corners, colors and effects. Usually those two are made in different parts of a webpage’s lifetime. The design is determined at the beginning and then you start filling it with content and keep the design fixed.
In CSS you just add the nifty
-tag I’ve told you about to the head of your HTML document and you have created a link to your design. In the HTML document you put content only, and that link of yours makes sure it looks right. You can also use the exact same link on many of your pages, giving them all of them the same design. You want to add content? Just write a plain HTML document and think about marking things up like ‘œheader’ instead of “big blue ‘header’and use CSS to make all headers look the way you want!Some examples of good and bad coding. What’s wrong with this?
<font size="3">Welcome to my page</font>
Comment: The font-tag is design and design shouldn’t be in the HTML document. All design should be in the CSS-file! Instead do this:
In the HTML:
<h1>Welcome to my page</h1>
In the CSS:
h1 { font-size: 2em; }
One more example:
<b>An error occurred</b>This looks right doesn’t it? But if you look up what stands for you quickly find bold. But bold is certainly design, so it still doesn’t belong in the HTML document. A better choice is
<em>
that stands for emphasis or simply “this piece of text is ‘important’. So instead of saying “this text looks like ‘this’ you are saying “this text is ‘important’ and you let the looks be decided by the CSS. Seems like a minor change, but it illustrates how to select your tags. Use this instead:
In the HTML:
<em>An error occured</em>
In the CSS:
em {
font-weight: bold;
color: Red;
}
One last example:
<table>
<tr>
<td><a href="">first link</a></td>
</tr>
<tr>
<td><a href="">second link</a></td>
</tr>
...
</table>Can CSS be used with other than HTML documents?
Yes. CSS can be used with any ny structured document format. e.g. XML, however, the method of linking CSS with other document types has not been decided yet.
Can Style Sheets and HTML stylistic elements be used in the same document?
Yes. Style Sheets will be ignored in browsers without CSS-support and HTML stylistic elements used.
What are pseudo-classes?
Pseudo-classes are fictional element types that do not exist in HTML. In CSS1 there is only one element type which can be classed this way, namely the A element (anchor). By creating three fictional types of the A element individual style can be attached to each class. These three fictional element types are: A as unvisited link, A as active link and A as visited link. Pseudo-classes are created by a colon followed by pseudo-class’s name. They can also be combined with normal classes,
e.g.:
A:link {background: black; color: white}
A:active {background: black; color: red}
A:visited {background: transparent; color: black}
<A HREF....>This anchor (or rather these anchors) will be displayed as declared above</A>
A.foot:link {background: black; color: white}
A.foft:active {background; black: color: red}
A.foot:visited {background: transparent; color: black}
<A CLASS=foot HREF....>This anchor and all other anchors with CLASS foot will be displayed as declared above</A>How do I design for backward compatibility using Style Sheets?
Existing HTML style methods (such as
CSS
img {display:block;}One problem that this can cause is when you want to have a few images next to each other - if they are block-level, they won’t be next to each other. To get around that, you can use float:left. Of course, this might present another problem - maybe you don’t want the image to float left. In this case, you can use an unordered list like this :
CSS ul, li { list-style-type:none; padding:0; margin:0 auto; } ul { width:150px; } li { float:left; } HTML < ul> <li><img src="wine.jpg" height="50" width="50" alt="wine" /></li> <li><img src="wine.jpg" height="50" width="50" alt="wine" /></li> <li><img src="wine.jpg" height="50" width="50" alt="wine" /></li> <li><img src="wine.jpg" height="50" width="50" alt="wine" /></li> <li><img src="wine.jpg" height="50" width="50" alt="wine" /></li> <li><img src="wine.jpg" height="50" width="50" alt="wine" /></li> <li><img src="wine.jpg" height="50" width="50" alt="wine" /></li> <li><img src="wine.jpg" height="50" width="50" alt="wine" /></li> <li><img src="wine.jpg" height="50" width="50" alt="wine" /></li> </ul>
Why use Style Sheets?
Style sheets allow a much greater degree of layout and display control than has ever been possible thus far in HTML. The amount of format coding necessary to control display characteristics can be greatly reduced through the use of external style sheets which can be used by a group of documents. Also, multiple style sheets can be integrated from different sources to form a cohesive tapestry of styles for a document. Style sheets are also backward compatible - They can be mixed with HTML styling elements and attributes so that older browsers can view content as intended.
What does the “Cascading” in “Cascading Style Sheets” mean?
Style Sheets allow style information to be specified from many locations. Multiple (partial) external style sheets can be referenced to reduce redundancy, and both authors as well as readers can specify style preferences. In addition, three main methods can be employed by an author to add style information to HTML documents, and multiple approaches for style control are available in each of these methods. In the end, style can be specified for a single element using any, or all, of these methods. What style is to be used when there is a direct conflict between style specifications for an element?
Cascading comes to the rescue. A document can have styles specified using all of these methods, but all the information will be reduced to a single, cohesive “virtual” Style Sheet. Conflict resolution is based on each style rule having an assigned weight according to its importance in the scheme of things. A rule with a higher overall importance will carry a higher weight. This will be used in place of a competing style rule with a lower weight/importance. A hierarchy of competing styles is thus formed creating a “cascade” of styles according to their assigned weights. The algorithm used to determine this cascading weight scale is fairly complex.
What is CSS rule ‘at-rule’?
There are two types of CSS rules: ruleset and at-rule. At-rule is a rule that applies to the whole style sheet and not to a specific selector only (like in ruleset). They all begin with the @ symbol followed by a keyword made up of letters a-z, A-Z, digits 0-9, dashes and escaped characters, e.g. @import or @font-face.
What is selector?
CSS selector is equivalent of HTML element(s). It is a string identifying to which element(s) the corresponding declaration(s) will apply and as such the link between the HTML document and the style sheet.
For example in P {text-indent: 10pt} the selector is P and is called type selector as it matches all instances of this element type in the document.
in P, UL {text-indent: 10pt} the selector is P and UL (see grouping); in .class {text-indent: 10pt} the selector is .class (see class selector).
What is CLASS selector?
Class selector is a “stand alone” class to which a specific style is declared. Using the CLASS attribute the declared style can then be associated with any HTML element. The class selectors are created by a period followed by the class’s name. The name can contain characters a-z, A-Z, digits 0-9, period, hyphen, escaped characters, Unicode characters 161-255, as well as any Unicode character as a numeric code, however, they cannot start with a dash or a digit. (Note: in HTML the value of the CLASS attribute can contain more characters).It is a good practice to name classes according to their function than their appearance.
.footnote {font: 70%} /* class as selector */
<ADDRESS CLASS=footnote/>This element is associated with the CLASS footnote</ADDRESS> <P CLASS=footnote>And so is this</P>
What is CSS declaration?
CSS declaration is style attached to a specific selector. It consists of two parts; property which is equivalent of HTML attribute, e.g. text-indent: and value which is equivalent of HTML value, e.g. 10pt. NOTE: properties are always ended with a colon.
What is ‘important’ declaration?
Important declaration is a declaration with increased weight. Declaration with increased weight will override declarations with normal weight. If both reader’s and author’s style sheet contain statements with important declarations the author’s declaration will override the reader’s.
BODY {background: white ! important; color: black}
In the example above the background property has increased weight while the color property has normal.
What is cascade?
Cascade is a method of defining the weight (importance) of individual styling rules thus allowing conflicting rules to be sorted out should such rules apply to the same selector.
Declarations with increased weight take precedence over declaration with normal weight:
P {color: white ! important} /* increased weight */
P (color: black} /* normal weight */
Are Style Sheets case sensitive?
No. Style sheets are case insensitive. Whatever is case insensitive in HTML is also case insensitive in CSS. However, parts that are not under control of CSS like font family names and URLs can be case sensitive - IMAGE.gif and image.gif is not the same file.
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