Dispatcherを要求されたので実装

/users/detail/123にアクセスした時に

/users/detail.html/123にアクセスを渡す.htaccess

# index access Normalization
RewriteEngine on

+ RewriteCond %{REQUEST_FILENAME} !-d
+ RewriteCond %{REQUEST_FILENAME} !-f
+ RewriteCond %{REQUEST_URI} ^/users/detail(/?|/(.*))$
+ RewriteRule ^(.*)$ /users/detail.html/$1 [L]

detail.html

var path = location.pathname; // /users/detail.html/123
var param = path.split('/');  // [users, detail.html, 123]
var contentsId = param[3];    // 123

detail.html側のJavaScriptでパラメータを取得できる

// パラメータ取得はPHPでも何でも良いぞ