A couple of things to keep in mind when you go this route...
In most browsers, it's easy to boost the font size as needed to make the presentation visible. You know how people doing projected presentations always make lame jokes about "reading the eye chart" because they put too much small-font text on their slides? With a browser, you can bump up the font size if this happens. Firefox or Safari: Ctrl-+ for Windows, Cmd-+ for OS X. (Although this is how those keyboard shortcuts are billed, you don't need the Shift key, so it ends up really being Ctrl/Cmd-=.)
I see live demos that bog down because the presenter spends a lot of time getting back to their original page, switching between tabs, looking for the right tab, or waiting for pages to load. Here are some tips for keeping the demo going at a reasonable pace:
Whatever is the main page of your demo/presentation, set up as many ways as you can to get back there quickly. Make it your home page, just until the presentation is over. Make it a "quick link" on the browser bookmark bar.
Browsers that can do tabs typically have a preference that doesn't have much use in day-to-day browsing. Firefox: When I open a link in a new tab, switch to it immediately. Safari: Select tabs and windows as they are created. Turn this setting on during the presentation. Every time you want to show what's behind another link, open the link in a new tab, which will immediately appear. (Windows: Ctrl-click. OS X: Cmd-click.) When finished with that page, close the tab and you'll instantly be back at your start page. (Windows: Ctrl-W. OS X: Cmd-W.)
When you're 10-20 seconds from the end of your spiel on one page, close it and open the next link. Wrap up that discussion, with the audience focus on your voice rather than the screen image, while the next page loads.
When you're whipping up the text of your presentation, the key point is to get it out fast. Presentation software is good for flowing text into templates with headings, paragraphs, and list bullets. To get the same kind of efficiency for text you'll slap on a web page, you can use Markdown, a text-to-HTML converter that lets you write in wiki-like style (start a line with a * to make it a bullet point, and so on).