css3 - CSS兼容写法问题

Question

::-webkit-scrollbar-thumb { //webkit前面为什么还有  ::    ？能去掉吗？？
    -webkit-border-radius: 15px;
    border-radius: 15px;
    background:rgba(200,200,200,0.7); 
    -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.5); 
}
我记得兼容性写法：
  -ms-
   -moz-
    -webkit-
     -o-
     这四个兼容性写法都卸载选择器的｛..｝内部，
     这里为什么选择器本身前面都有-webkit-？而且-webkit-前面还有 “::”能去掉吗？

Answer 1

:: is a pseudo-object selector, which is different from the pseudo-class selector :. You can read the manual: http://gucong3000.github.io/css-book/selectors/pseudo-element/after.htm

-webkit- is a private attribute of Chrome browser, similar to Firefox's -moz and IE's -ms

Answer 2

http://www.w3school.com.cn/cssref/selector_selection.asp