The background of the sidebar grows downward as the main content grows downward
method one:
You need to set a fixed height for the parent "mainLeft" of "leftDown" first. The height should be greater than the maximum display height of the main content. The height of "leftDown": 100%
Method Two:
Give the div of the main content a fixed height, the height of "mainLeft" is relatively fixed, and the height of "leftDown": 100%
Method three:
Give the div of the main content a uniform background color, and set the background of the area on the right that does not need a background color to white, then the background color of the remaining "mainLeft" is obtained.
When the parent div is set to overflow:hidden;, the effect of the drop-down list with events will be incomplete, and the overflowing part will be hidden. At this time, the height of the parent div needs to be set to a fixed height
Generally, the div of the top bar does not give a fixed width, only the height and background, but when the page percentage is enlarged, the content inside the div will exceed, resulting in the background of the div cannot be extended to the right, here you need to give div{min-width: (not less than the fixed width value of the inner div container);}