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 3x3 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 <link>-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 “header” 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 <b> 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 <font SIZE> and <b>) may be easily combined with style sheet specification methods. Browsers that do not understand style sheets will use the older HTML formatting methods, and style sheets specifications can control the appearance of these elements in browsers that support CSS1.

 

As a reader, how can I make my browser recognize my own style sheet?

Netscape
It is not possible to do this in Netscape yet (as of version 4.0.)
Internet Explorer 3.0 (Win95/NT)
[It is possible to do this at least in Windows95/NT, but no user interface is provided. Unknown how this might be accomplished on other operating systems.]

1. Open the Registry editor (Start..Run..regedit..ENTER)
2. Under the 'HKEY_LOCAL_MACHINE\Software\Microsoft\InternetExplorer\Styles' key, Edit..New..String Value
3. The new value should be called 'StyleSheet Pathname'
4. For the value, type in the full directory path of your .css style sheet.

Internet Explorer 4.0 (Win95/NT)

1. Under the View menu, select 'Internet Options'.
2. Under the 'General' tab, choose the 'Accessibility' button.
3. Choose the 'Format documents using my style sheet' check box and 'Browse...' to the location of your .css style sheet.

MySQL - MySQL Extensions to ANSI SQL92
MySQL includes some extensions that you probably will not find in other SQL databases. Be warned that if you use them, your code will not be portable to other SQL servers. In some cases, you can write code that includes MySQL extensions, but is still portable, by using comments of the form /*! ... */. In this case, MySQL will parse and execute the code within the comment as it would any other MySQL statement, but other SQL servers will ignore the extensions. For example:

SELECT /*! STRAIGHT_JOIN */ col_name FROM table1,table2 WHERE ...

If you add a version number after the '!', the syntax will only be executed if the MySQL version is equal to or newer than the used version number:

CREATE /*!32302 TEMPORARY */ TABLE (a int);

The above means that if you have Version 3.23.02 or newer, then MySQL will use the TEMPORARY keyword.

MySQL extensions are listed below:

The field types MEDIUMINT, SET, ENUM, and the different BLOB and TEXT types.
The field attributes AUTO_INCREMENT, BINARY, NULL, UNSIGNED, and ZEROFILL.
All string comparisons are case insensitive by default, with sort ordering determined by the current character set (ISO-8859-1 Latin1 by default). If you don't like this, you should declare your columns with the BINARY attribute or use the BINARY cast, which causes comparisons to be done according to the ASCII order used on the MySQL server host.
MySQL maps each database to a directory under the MySQL data directory, and tables within a database to filenames in the database directory. This has a few implications:
Database names and table names are case sensitive in MySQL on operating systems that have case-sensitive filenames (like most Unix systems).
Database, table, index, column, or alias names may begin with a digit (but may not consist solely of digits).
You can use standard system commands to backup, rename, move, delete, and copy tables. For example, to rename a table, rename the `.MYD', `.MYI', and `.frm' files to which the table corresponds.
In SQL statements, you can access tables from different databases with the db_name.tbl_name syntax. Some SQL servers provide the same functionality but call this User space. MySQL doesn't support tablespaces as in: create table ralph.my_table...IN my_tablespace.
LIKE is allowed on numeric columns.
Use of INTO OUTFILE and STRAIGHT_JOIN in a SELECT statement.
The SQL_SMALL_RESULT option in a SELECT statement.
EXPLAIN SELECT to get a description on how tables are joined.
Use of index names, indexes on a prefix of a field, and use of INDEX or KEY in a CREATE TABLE statement.
Use of TEMPORARY or IF NOT EXISTS with CREATE TABLE.
Use of COUNT(DISTINCT list) where 'list' is more than one element.
Use of CHANGE col_name, DROP col_name, or DROP INDEX, IGNORE or RENAME in an ALTER TABLE statement.
Use of RENAME TABLE.
Use of multiple ADD, ALTER, DROP, or CHANGE clauses in an ALTER TABLE statement.
Use of DROP TABLE with the keywords IF EXISTS.
You can drop multiple tables with a single DROP TABLE statement.
The LIMIT clause of the DELETE statement.
The DELAYED clause of the INSERT and REPLACE statements.
The LOW_PRIORITY clause of the INSERT, REPLACE, DELETE, and UPDATE statements.
Use of LOAD DATA INFILE. In many cases, this syntax is compatible with Oracle's LOAD DATA INFILE.
The ANALYZE TABLE, CHECK TABLE, OPTIMIZE TABLE, and REPAIR TABLE statements.
The SHOW statement.
Strings may be enclosed by either `"' or `'', not just by `''.
Use of the escape `\' character.
The SET OPTION statement.
You don't need to name all selected columns in the GROUP BY part. This gives better performance for some very specific, but quite normal queries.
One can specify ASC and DESC with GROUP BY.
To make it easier for users who come from other SQL environments, MySQL supports aliases for many functions. For example, all string functions support both ANSI SQL syntax and ODBC syntax.
MySQL understands the || and && operators to mean logical OR and AND, as in the C programming language. In MySQL, || and OR are synonyms, as are && and AND. Because of this nice syntax, MySQL doesn't support the ANSI SQL || operator for string concatenation; use CONCAT() instead. Because CONCAT() takes any number of arguments, it's easy to convert use of the || operator to MySQL.
CREATE DATABASE or DROP DATABASE.
The % operator is a synonym for MOD(). That is, N % M is equivalent to MOD(N,M). % is supported for C programmers and for compatibility with PostgreSQL.
The =, <>, <= ,<, >=,>, <<, >>, <=>, AND, OR, or LIKE operators may be used in column comparisons to the left of the FROM in SELECT statements. For example:
mysql> SELECT col1=1 AND col2=2 FROM tbl_name;


The LAST_INSERT_ID() function.
The REGEXP and NOT REGEXP extended regular expression operators.
CONCAT() or CHAR() with one argument or more than two arguments. (In MySQL, these functions can take any number of arguments.)
The BIT_COUNT(), CASE, ELT(), FROM_DAYS(), FORMAT(), IF(), PASSWORD(), ENCRYPT(), md5(), ENCODE(), DECODE(), PERIOD_ADD(), PERIOD_DIFF(), TO_DAYS(), or WEEKDAY() functions.
Use of TRIM() to trim substrings. ANSI SQL only supports removal of single characters.
The GROUP BY functions STD(), BIT_OR(), and BIT_AND().
Use of REPLACE instead of DELETE + INSERT.
The FLUSH flush_option statement.
The possiblity to set variables in a statement with :=:
SELECT @a:=SUM(total),@b=COUNT(*),@a/@b AS avg FROM test_table;
SELECT @t1:=(@t2:=1)+@t3:=4,@t1,@t2,@t3;