Content is essential; presentation an afterthought. Content is unchanging, change being intrinsic to presentation. Content endures, while presentation(s) may come and go.

Presentation assures visibility, recognition, attention; content may be, on its own, unappealing to the eye. Presentation helps the content communicate-get across to the reader-what it has to say; content, without presentation, may fail to do so. Presentation is aware of its audience(s) and publication(s), and may modify its visual approach(es) accordingly; content is largely ignorant of these contexts (excepting perhaps writing style).

CSS is designed primarily to enable the separation of document content (written in HTML or a similar markup language) from document presentation, including elements such as the colors, fonts, and layout. This separation can improve content accessibility, provide more flexibility and control in the specification of presentation characteristics, enable multiple pages to share formatting, and reduce complexity and repetition in the structural content (such as by allowing for tableless web design).

You can see the examples of CSS in the following website which contains the standardized websites made with CSS...

www.cssmania.com

Multimedia content relates to multiple mediums in a single presentation. For instance, a presentation can include text, video, images, and physical objects.

You can begin a presentation best by outlining the content of your presentation, introducing yourself and establishing a link with the audience. The latter can be done by e.g. thanking them for being at your presentation.

Stylesheets are used to format the HTML content. They separate the content from the presentation of the content.