Relationship between. skin and css in Theme

I have read ASP. NET 2.0 Theme textbooks just now. Here is an example: there are two textbox, but one is server control and the other is html input.
According to the teaching material, the former is white backcolor, and the latter is black backcolor.
However, both of them are black backcolor.
As a result, I began to wonder if the version vs2005 is different from the version mentioned in the textbook. I also searched the internet for the reason.
In view of the fact that I have made several mistakes before and did not carefully read the code, this time I am not persistent in searching online and asking questions on forums and QQ groups. Copy the code of the teaching material to the related ITEM in vs2005, and compare the words. The teaching material is one more"BackColor = "# ffffff"".
    
As a summary, the relationship between css and. skin on control is my personal understanding. If you have any mistakes, please point out. Thank you.

12.16.skinpriority is higher than .css, but it is invalid for html control.
2. When. skin does not describe the server control attributes (even if it is not described, for example, BackColor under textbox .),. Css affects server control (for example, BackColor ).