If your dropdowns are this long, you might wanna take a re-look at your navigational strategy. But, if it makes sense, a technique like this may be beneficial.
PROBLEM: Dropdown menu goes down below the fold when opened, making lower items inaccesible.
SOLUTION? Make menu scroll up and down as you mouse through it.
来源： Chris Coyier 代码整理：脚本之家 感谢：好图
转载请注明出处，此代码仅供学习交流，请勿用于商业用途。