We usually add one stylesheet to out HTML code but an HTML document doesn’t need to have a single style sheet.
We can have a default style for the HTML page and any number of alternatives stylesheets for the reader to choose from.
Why to use it?
It provides few options for users to choose from. Users can select any version of a page, based on their preferences.
The browser decided on which alternatives styles the reader can choose and not every browsers or version of browsers supports it but many of them do.
In Opera and Firefox we can find the styles under the “View” menu. Chrome versions 1-48 don’t support it at all but we can add an extension to it to make it support the alternate stylesheets. Checkout the compatibility report on MDN.
Here is the screen capture from Mozilla.
To include extra style sheets, we need to add more LINK tags in the header, with the correct REL and TITLE attributes.
In the example above, the first stylesheet “main.css” will be applied to the HTML page no matter what.
From next 3 listed stylesheets, style_1 will be on the default selected in the browser menu. User can select any stylesheet from those 3 styles.