After updating the OSX to the latest one.
update-to-el-capitan

My webserver didn’t recognize my previously customized VHOST.
Turn out,the update saved those config as ~previous.
So, I just need to restore it back and it is online again.

Thanks.

nb-namran:/etc/apache2$ diff httpd.conf httpd.conf~previous 
160c160
< #LoadModule vhost_alias_module libexec/apache2/mod_vhost_alias.so
---
> LoadModule vhost_alias_module libexec/apache2/mod_vhost_alias.so
166c166
< #LoadModule userdir_module libexec/apache2/mod_userdir.so
---
> LoadModule userdir_module libexec/apache2/mod_userdir.so
168,169c168,169
< #LoadModule rewrite_module libexec/apache2/mod_rewrite.so
< #LoadModule php5_module libexec/apache2/libphp5.so
---
> LoadModule rewrite_module libexec/apache2/mod_rewrite.so
> LoadModule php5_module libexec/apache2/libphp5.so
183a184,185
> #User admin
> #Group staff
258c260,261
<     AllowOverride None
---
>     #AllowOverride None
>     AllowOverride All
263a267,269
>     	#Order deny,allow
> 	#Deny from all
> 	#Allow from all
493c499
< #Include /private/etc/apache2/extra/httpd-userdir.conf
---
> Include /private/etc/apache2/extra/httpd-userdir.conf
499c505
< #Include /private/etc/apache2/extra/httpd-vhosts.conf
---
> Include /private/etc/apache2/extra/httpd-vhosts.conf
528a535,545
> #
> # uncomment out the below to deal with user agents that deliberately
> # violate open standards by misusing DNT (DNT *must* be a specific
> # end-user choice)
> #
> #<IfModule setenvif_module>
> #BrowserMatch "MSIE 10.0;" bad_DNT
> #</IfModule>
> #<IfModule headers_module>
> #RequestHeader unset DNT env=bad_DNT
> #</IfModule>

after restore the config,you may need to restart the apache2 server with the following command.

apachectl restart