Question about vertical center of div due to error 12306 _ html/css_WEB-ITnose

Due to the vertical center problem of div due to 12306 errors, I want to see if there are still no remaining tickets when I go home on New Year's Day. I opened 12306 secretly and started to query the tickets for returning home. I found that I could not query them, an error occurred while checking again.

Seeing this is very depressing and tangled, But I suddenly thought that I had been trying to center p vertically recently. I tried a website as large as 12306 and it must be vertically centered,

After a try, I was not disappointed and adapted to the vertical center of various resolutions.

Great. Right-click the source code.

P class = "err_text">
 
 
                         
  
  
 
                                                  
  
  
Network problems may exist. Please try again!
 
 

Then let's take a look at how css is written.

.err_text{    position:absolute;    margin-top:-159px;        top:50%;    left:50%;    margin-left:-247px;    width:495px;    height:282px;}#error{    width:495px;    margin-left:auto;    margin-right:auto;    list-style:none;}#error li{    list-style:none;}#err_top{    background:url(err_top.gif) no-repeat;    height:78px;    line-height:78px;    width:495px;    }#err_bot{    background:url(err_bot.gif) no-repeat;    height:204px;    padding-top:50px;    width:495px;        text-align:center;    font-size:14px;    font-weight:bold;}

At this time, you will surely find that the key code is actually top: 50%, left: 50%. Of course, the premise is absolute positioning, so that you can center it.