1. The ul tag has a padding value by default in Mozilla, but in IE only margin has a value.
2. The same class selector can appear repeatedly in a document, but the id selector can only appear once; use class and id at the same time for CSS definition of a label. If the definition is repeated, id The definition of the selector is valid because the weight of ID is greater than CLASS.
3. A stupid way to adjust compatibility (IE and Mozilla): Beginners may encounter such a situation: it is normal for the same label attribute to be displayed as A in IE, but it must be displayed in Mozilla. It must be set to B to display normally, or the two are reversed. Temporary solution: selector {attribute name: B !important; attribute name: A}
4. If some spacing is needed between a group of tags to be nested, leave it to the tags inside. margin attribute instead of defining the padding of the outer label
5. It is recommended to use background-image instead of list-style-image for the icon in front of the li tag.
6. IE cannot distinguish the difference between inheritance relationship and father-son relationship. They are all inheritance relationships.
7. When adding selectors to your tags, don’t forget to add comments to the selectors in CSS. You'll know why you do this when you modify your CSS later.
8. If you set a dark background image and bright text effect for a label. It is recommended to set a darker background color for your label at this time.
9. Pay attention to the order when defining the four states of a link: Link Visited Hover Active
10. Please use background
11. The defined color can be abbreviated #8899FF=#89F12. Table performs much better than other tags in some aspects. Please use it where column alignment is required.
13.