Web standardization advocates the use of DIV+CSS to lay out web structure. When using CSS to plan web pages, there are many ways to effectively and reasonably compress the code, and the advantage of this is that it is convenient for designers to maintain and view, and to "slim" the code page, thereby speeding up the loading speed of the page.
As for some abbreviated "slimming" techniques in CSS, I will not say here; Here we recommend two good online compression (optimization) CSS code sites.