The level-2 drop-down menu is hidden, and css setting of z-index does not work in ie. Solution

JQuery makes a second-level menu with a mouse and adds an animation effect. firefox is perfectly rendered. Some drop-down menus under IE will be covered by the following webpage content, such as iframe, div, and drop-down box, input box, etc.

The result of setting the z-index in ie does not have any effect, and the jQuery plug-in bgiframe is integrated. The result can only solve the selection box under ie6. I was dizzy by the z-index bug of IE. I have done it several times. Note:

1. Pay attention to SettingsZ-index (Because z-index has inheritance, stacking context, stacking level)
2. the position: relative/absolute must be specified.
3. If the value of z-index is negative, different browsers may behave differently. google does not need a negative value.