Learning Standards - Notes_Experience Exchange

A few points I summarized:
1. If an object has float, width will basically not be used
2. Sometimes there are requirements for the writing order of divs. Write float first
3. Finally understand IE Why I hate it so much

An example of three columns, the middle column is adaptive
There is a problem here, that is, there will be a small gap between the three columns, which does not exist under FF, so if you want to form For continuous effects, you can define the background in main.