"Stretch text" can be a part of a Web page that is collapsed and expanded or a separate Web page that is shown inline in another. (You can think of it as making the A element behave as an OBJECT.)

Pop-ups are Web pages that are displayed in a temporary window. It is possible with JavaScript, but not yet with style sheets.

Aligning text with tab stops is often simpler than with tables and it allows text to wrap at the end of the line, while also being aligned. For example, the author of a citation can be shown right-aligned on the last line of the citation.

Highlighting the target is part of the Selectors module of CSS3, but is not yet implemented by Opera.

Buttons, selection lists, etc. contain text, but I cannot select the text for cut & paste. That is a limitation in the graphics toolkit (Qt), not Opera itself, but it would be nice if it could be changed.

Normal hyperlinks show the URL in the status bar and allow me to copy the URL to the clipboard, but the URLs of forms remain hidden.

The address bar shows the URL of the current document and I can use that to copy and paste the URL into a document of my own. But it is very hard to get the URLs that point to anchors in the document. Amaya has a mode where such local anchors are represented by icons, so their URLs can be copied.

Fish search was an extension to Mosaic back in 1994. It extends the "search in this page" to "search in this page and all linked pages." The maximum depth wass 4, which is usually already too much, but it would help with finding text in articles that are split over multiple pages.

Most browsers have a source view, but it opens a new window. That is sometimes what I want, but usually displaying the source in the same window would be both quicker and less wasteful of screen space.

Mozilla now uses the LINK elements in HTML to build a navigation menu. That is about 12 years after Lynx, I guess, but better late than never. When more browsers support it, many of the navigation menus that take up so much space on the page and that are so inconsistent can be removed. Moreover, the body of a page will then really only contains information about the subject of the page and not about the rest of the site.