[1] Opera Reader: Paging the Web (2015-07-28 11:59:24 +09:00 版) http://people.opera.com/howcome/2011/reader/#navigation

The new at-rule – @-o-navigation – can look something like thhis:
@-o-navigation {
nav-up: -o-url-doc(/);
nav-down: url(a1.html);
nav-right: -o-link-rel(next);
nav-left: -o-go(back);
}
The four new properties are pretty self explanatory – nav-up is what you want to navigate to when the page is moved up, and so on. Let's now talk through the four different values that the properties can take:
-o-url-doc(path): The path specified is a relative path to the HTML document, for example / to go to the root document.
url(path): The path specified is a standard URL to a file, and can be of any type that url() normally accepts (for example in background-image: url();).
-o-link-rel(value): The value is a rel attribute value from a <link> element. For example, when you specify next, the browser looks for a <link> element in the <head>, and then takes its href value as the document to navigate to.
-o-go(value): in this case, the value can be forward or back – these instruct the browser to go forward or back in its history.