Set - 2

Question 11 :

Three selectors: h1, .warning and #footer, what they do ?

Answer :

An element points at a HTML-tag somewhere on your page. In the example above we want to style the <h1>-tag. Note that using an element like that affects all tags with that name, so using p { margin-left: 100px; } gives all <p>-tags a left-margin. 
Using a class is just as simple. When writing .your_class you style all tags with a class with the name "your_class". In the example above we have .warning which will style e.g. <div class="warning"> and <em class="warning">, that is, any element with the class warning. Classes are used when you want to style just a few of your tags in a way, perhaps you want some of your links red? Add a class to all those links. 
You need one more building block: the id. This time you style an element with the attribute "id" set to the id you have chosen. Ids work exactly like classes except for one thing; you can only have one id with a certain name in each of your HTML documents. In the example above we style <div id="footer">. If you look at the example it does make sense: a HTML document may contain several warnings but only one footer. Ids should be used when you want to style just one specific tag. 
Using those three building blocks will take you far but when you get to more advanced layouts you might want to combine the building blocks into more advanced selectors. Just to give you two examples of what you can do: em.warning to style only those <em>-tags with the class .warning set. You can also use #footer a to style only the links that are nested inside the tag with id "footer. 
Each of the selectors has a set of declarations tied to them. Each declaration has a property, describing what we want to change and a value, what we should change it to. An example: a { color: Blue; font-size: 3em; }. You have the selector a there, so all links in your document will be styled. We have two declarations: color: Blue and font-size: 3em;. Lastly each declaration consists of two parts: the property color and the value Blue. 
there is a LOT of things you can style and play with. Additionally (close to) all tags are equal in CSS, so you can set e.g. borders and colors of any element just like you could with a table if you used only HTML.


Question 12 :

What is CSS rule 'ruleset'?

Answer :

There are two types of CSS rules: ruleset and at-rule. Ruleset identifies selector or selectors and declares style which is to be attached to that selector or selectors. For example

P {text-indent: 10pt} is a CSS rule. CSS rulesets consist of two parts: selector, e.g. P and declaration, e.g. {text-indent: 10pt}.

P {text-indent: 10pt} - CSS rule (ruleset)
{text-indent: 10pt} - CSS declaration
text-indent - CSS property
10pt - CSS value


Question 13 :

'Fixed' Background? 

Answer :

There is the possibility to use the HTML tag bgproperties="fixed", but that is IE proprietary, and dependent upon the 'background' attribute (deprecated in HTML4).
With CSS, you can declare the background like:

BODY {
    font-family : "Trebuchet MS", Verdana, Arial, Helvetica, sans-serif;
    background-image: url(images/yourimage.gif);
    background-repeat: no-repeat; /*no-tiling background*/
    background-position: center;
    background-attachment: fixed;
    background-color: #hexcolor;
    color : #hexcolor;
    margin: 10px;
}

that shows a background-image in the center of the <BODY> element, non-scrolling and non-repeating - in IE or NN6. NN 4.xx gets the non-repeat-part right, but stuffs the picture in the upper left corner and scrolls ...


Question 14 :

What is embedded style? How to link?

Answer :

Embedded style is the style attached to one specific document. The style information is specified as a content of the STYLE element inside the HEAD element and will apply to the entire document.

<HEAD>
<STYLE TYPE="text/css">
<!--
P {text-indent: 10pt}
-->
</STYLE>
</HEAD>

Note: The styling rules are written as a HTML comment, that is, between <!-- and --> to hide the content in browsers without CSS support which would otherwise be displayed.


Question 15 :

What is ID selector? 

Answer :

ID selector is an individually identified (named) selector to which a specific style is declared. Using the ID attribute the declared style can then be associated with one and only one HTML element per document as to differentiate it from all other elements. ID selectors are created by a character # followed by the selector'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.

#abc123 {color: red; background: black}
<P ID=abc123>This and only this element can be identified as abc123 </P>