I am involved in the div+css layout design since it is so popular and is becoming standard for web front end UI design. Today I reread thru the 9th section of CSS2 on w3.org. this section is focus on the visual formatting model one of which is about positioned element typically about relative&absolute position. Here are several important statements excerpt from this section.

1. The containing block of one positioned box is established by the nearest positioned ancestor, or if none exists, the initial containing block.

so what's a positioned box? normally it is a block element like div with position css style attribute set to non static value. What's initial containing block? also in the above doc, it says the root of document tree generates the containing block, aka initial containing block.

2. In CSS2.1, a box may be laid out according three positioning schemes, normal flow, float and absolutely positioning.  the relative positioning is included in the normal flow scheme, in the absolute positioning scheme, a box is removed from the normal flow entirely and assigned a position with respect to its containing block.

 

During development of our management system, I built an utility class to read sql statement from several xml files. Each function module of system will be stored as one standlone file as such to ease maintenance task. In each file, I predefined sql statement schema for stored procedures and ordinary statements. To be concreate, each statement will correspond to one single element which has several attributes to describe its functionality and comments and has child element called params which has cascading child element param which in turn has four attribute to describe the parameter's name, size, type. All these seemed good and it worked fine for now.  The problem was I used string value to assign this type attribute, though data type can be CLR's, can be SqlServer's, can be data provider's. Which one I should choose wisely?  Today, I reread from MSDN about data type of CLR & native data type of SQL Server 2005 & mapped data type of Sqlserver data provider. Here I exepted some important words for memo:

The System.Data.SqlTypes namespace provide class for native data type of Sql Server, such as SqlDecimal, SqlDateTime, SqlString. The classes under this namespace have corresponding native data type of Sql Server and yield better performance than SqlDbType enumeration since behind the scene those data type conversion used SqlXXX types.

It's clear now.