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XHTML : 

XHTML Introduction to CSS

Applying CSS : 

2 Applying CSS There are three ways of applying CSS to HTML: In-line Internal/Embedded External/Linked

Inline Styles : 

3 Inline Styles In-line styles are plonked straight into the HTML tags using the style attribute. They look something like this: <p style="color: red">text</p> This will make that specific paragraph red. The ideal is that the HTML should be a stand-alone, presentation free document, and so in-line styles should be avoided wherever possible.

Internal Styles : 

4 Internal Styles Internal styles are used for the whole page. Inside the head tags, the style tag surrounds all of the styles for the page. <html> <head><title>CSS Example</title> <style type="text/css"> p { color: red; } a { color: blue; } </style> ...

Internal Styles : 

5 Internal Styles This will make all of the paragraphs in the page red and all of the links blue. Similarly to the in-line styles, you should keep the HTML and the CSS files separate, and so we are left with our saviour...

External Styles : 

6 External Styles External styles are used for the whole, multiple-page website. There is a separate CSS file, which will simply look something like: p { color: red; } a { color: blue; }

External Styles : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 7 External Styles If this file is saved as 'web.css' then it can be linked to in the HTML like this: <html> <head> <title>CSS Example</title> <link rel="stylesheet" type="text/css“ href="web.css" /> ...

Selectors, Properties and Values : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 8 Selectors, Properties and Values Whereas HTML has tags, CSS has 'selectors'. Selectors are the names given to styles in internal and external style sheets. Selectors are simply the names of HTML tags and are used to change the style of a specific tag. For each selector there are 'properties' inside curly brackets, which simply take the form of words such as color, font-weight or background-color. A value is given to the property following a colon (NOT an 'equals' sign) and semi-colons separate the properties.

Selectors, Properties and Values : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 9 Selectors, Properties and Values body { font-size: 0.8em; color: navy; } This will apply the given values to the font-size and color properties to the body selector. So basically, when this is applied to an HTML document, text between the body tags (which is the content of the whole window) will be 0.8 ems in size and navy in colour.

Lengths and Percentages : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 10 Lengths and Percentages There are many property-specific units for values used in CSS, but there are some general units that are used in a number of properties and it is worth familiarising yourself with these before continuing. 'em' (such as font-size: 2em) is an element approximately equal to the height of a character. 'px' (such as font-size: 12px) is the unit for pixels. 'pt' (such as font-size: 12pt) is the unit for points. '%' (such as font-size: 80%) is the unit for... wait for it... percentages.

Lengths and Percentages : 

11 Lengths and Percentages Other units include 'pc' (picas – 1/6 of an inch), 'cm' (centimetres), 'mm' (millimetres) and 'in' (inches). When a value is zero, you do not need to state a unit. For example, if you wanted to specify no border, it would be border: 0.

Lengths and Percentages : 

12 Lengths and Percentages Note: A web page is not a static, absolute medium. It is meant to be flexible and the user should be allowed to view the web page how the hell they like, which includes the font size AND the size of the screen. Because of this, it is generally accepted that 'em' or '%' are the best units to use for font-sizes, rather than 'px', which leads to non-resizable text in most browsers, and should be used sparingly, for border sizes for example.

Colours : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 13 Colours CSS brings 16,777,216 colours to your disposal. They can take the form of a name, an 'rgb' (red/green/blue) value or a 'hex' code. redIs the same asrgb(255,0,0)Which is the same asrgb(100%,0%,0%)Which is the same as#ff0000Which is the same as#f00

Colours : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 14 Colours There are 16 valid predefined colour names. These are aqua, black, blue, fuchsia, gray, green, lime, maroon, navy, olive, purple, red, silver, teal, white, and yellow. Transparent is also a valid value. The 3 values in the rbg value are from 0 to 255, 0 being the lowest level (e.g. no red), 255 being the highest level (e.g. full red). The values can also be a percentage. Hexadecimal (previously and more accurately known as 'sexadecimal') is a base-16 number system. We are generally used to the decimal number system (base-10, from 0 to 9), but hexadecimal has 16 digits, from 0 to f.

Colours : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 15 Colours The hex number is defined by a hash character (#) and can be three or six digits in length. Basically, the three-digit version is a compressed version of the six-digit (#f00 becomes #ff0000, #c96 becomes #cc9966 etc.). The three-digit version is easier to decipher (the first digit, like the first value in rgb, is red, the second green and the third blue) but the six-digit version gives you more control over the exact colour.

'color' and 'background-color' : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 16 'color' and 'background-color' Colours can be applied by using color and background-color (note that this must be the American English 'color' and not 'colour'). A blue background and yellow text could look like this: h1 { color: yellow; background-color: blue; } These colours might be a little too harsh, so you could change the code of your CSS file for slightly different shades:

'color' and 'background-color' : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 17 'color' and 'background-color' body { font-size: 0.8em; color: navy; } h1 { color: #ffc; background-color: #009; } You can apply the color and background-color properties to most HTML elements, including body, which will change the colours of the page and everything in it.

Text : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 18 Text You can alter the size and shape of the text on a web page with a range of properties, outlined below: font-family font-size font-weight font-style text-decoration text-transform Text Spacing

font-family : 

19 font-family This is the font itself, such as 'Times New Roman', 'Arial' or 'Verdana'. The font you specify must be on the user's computer, so there is little point in using obscure fonts. There are a select few 'safe' fonts (the most commonly used are arial, verdana and times new roman) But you can specify more than one font, separated by commas. The purpose of this is that if the user does not have the first font you specified, the browser will go through the list until it finds one it does have. This is useful because different computers sometimes have different fonts installed.

font-family : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 20 font-family So font-family: arial, helvetica, for example, is used so that similar fonts are used on PC (which usually has arial, but not helvetica) and Apple Mac (which does not usually have arial, and so helvetica, which it does normally have, will be used). Note: if the name of a font is more than one word, it should be put in quotation marks, such as font-family: "Times New Roman".

font-size : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 21 font-size The size of the font. Be careful with this - text such as headings should not just be a paragraph in a large font; you should still use headings (h1, h2 etc.) even though, in practice, you could make the font-size of a paragraph larger than that of a heading (not recommended for sensible people).

font-weight : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 22 font-weight This states whether the text is bold or not. In practice this usually only works as font-weight: bold or font-weight: normal. In theory it can also be bolder, lighter, 100, 200, 300, 400, 500, 600, 700, 800 or 900, but seeing as many browsers shake their heads and say 'I don't think so', it's safer to stick with bold and normal.

font-style : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 23 font-style This states whether the text is italic or not. It can be font-style: italic or font-style: normal.

text-decoration : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 24 text-decoration This states whether the text is underlined or not. This can be: text-decoration: overline, which places a line above the text. text-decoration: line-through, strike-through, which puts a line through the text. text-decoration: underline SHOULD ONLY BE USED FOR LINKS because users generally expect underlined text to be links. This property is usually used to decorate links, such as specifying no underline with text-decoration: none.

text-transform : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 25 text-transform This will change the case of the text. text-transform: capitalize turns the first letter of every word into uppercase. text-transform: uppercase turns everything into uppercase. text-transform: lowercase turns everything into lowercase. text-transform: none I'll leave for you to work out.

Text : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 26 Text body { font-family: arial, helvetica, serif; font-size: 0.8em; } h1 { font-size: 2em; } h2 { font-size: 1.5em; } a { text-decoration: none; } strong { font-style: italic; text-transform: uppercase; }

Text Spacing : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 27 Text Spacing The letter-spacing and word-spacing properties are for spacing between letters or words. The value can be a length or normal. The line-height property sets the height of the lines in an element, such as a paragraph, without adjusting the size of the font. It can be a length, a percentage or normal.

Text Spacing : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 28 Text Spacing The text-align property will align the text inside an element to left, right, center or justify. The text-indent property will indent the first line of a paragraph to a given length or percentage. This is a format usually used in print, and rarely in digital media such as the web.

Text Spacing : 

29 Text Spacing p { letter-spacing: 0.5em; word-spacing: 2em; line-height: 1.5em; text-align: center; }

Margins and Padding : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 30 Margins and Padding margin and padding are the two most commonly used properties for spacing-out elements. A margin is the space outside of the element, whereas padding is the space inside the element. h2 { font-size: 1.5em; background-color: #ccc; margin: 1em; padding: 3em; }

Margins and Padding : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 31 Margins and Padding You will see that this leaves one-character width space around the secondary header and the header itself is fat from the three-character width padding. The four sides of an element can also be set individually. margin-top, margin-right, margin-bottom, margin-left, padding-top, padding-right, padding-bottom and padding-left are the self-explanatory properties you can use.

The Box Model : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 32 The Box Model Margins, padding and borders (later) are all part of what's known as the Box Model. The Box Model works like this: in the middle you have the element box (let's say an image), surrounding that you have the padding box, surrounding that you have the border box and surrounding that you have the margin box. It can be visually represented like this: The box model can be applied to every element on the page.

Borders : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 33 Borders Borders can be applied to most HTML elements within the body. To make a border around an element, all you need is border-style. The values can be solid, dotted, dashed, double, groove, ridge, inset and outset. border-width sets the width of the border, which is usually in pixels. There are also properties for border-top-width, border-right-width, border-bottom-width and border-left-width. Finally, border-color sets the colour.

Borders : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 34 Borders h2 { border-style: dashed; border-width: 3px; border-left-width: 10px; border-right-width: 10px; border-color: red; } This will make a red dashed border around all HTML secondary headers (the h2 element) that is 3 pixels wide on the top and bottom and 10 pixels wide on the left and right (these having over-ridden the 3 pixel wide width of the entire border).

Putting It All Together : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 35 Putting It All Together You should download the HTML file cssintro.htm and add the line that we added at the start of this lecture, linking the HTML file to the CSS file. The code that follows covers all of the CSS methods in this lecture. If you copy and paste this into notepad and save it as your CSS file and look at the HTML file then you should now understand what each CSS property does and how to apply them. The best way to fully understand all of this is to mess around with the HTML and the CSS files and see what happens when you change things.

CSS Code : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 36 CSS Code body { font-family: arial, helvetica, sans-serif; font-size: 80%; color: black; background-color: #ffc; margin: 1em; padding: 0; } /* By the way, this is a comment */ p { line-height: 1.5em; }

CSS Code (cont.) : 

37 CSS Code (cont.) h1 { color: #ffc; background-color: #900; font-size: 2em; margin: 0; margin-bottom: 0.5em; padding: 0.25em; font-style: italic; text-align: center; letter-spacing: 0.5em; border-bottom-style: solid; border-bottom-width: 0.5em; border-bottom-color: #c00; }

CSS Code (cont.) : 

©Nina Bresnihan, Dept. of Computer Science, TCD 2004 38 CSS Code (cont.) h2 { color: white; background-color: #090; font-size: 1.5em; margin: 0; padding: 0.1em; padding-left: 1em; } h3 { color: #999; font-size: 1.25em; }

CSS Code (cont.) : 

39 CSS Code (cont.) img { border-style: dashed; border-width: 2px; border-color: #ccc; } a { text-decoration: none; } strong { font-style: italic; text-transform: uppercase; }

CSS Code (cont.) : 

40 CSS Code (cont.) li { color: #900; font-style: italic; } table { background-color: #ccc; }