Simply stated, sIFR is a SEO friendly way to use your custom fonts, without the need to use an Image. It’s a search engine friendly method for using your custom fonts.
While most people simply create images when they need a custom-type font, sIFR can dynamically create short text blocks using whatever font you want (while still rendering the text with a default font on non-Flash browsers). In general, if you want to utilize better typography, while maintaining the optimization of your H1 tags… sIFR might be the easiest way to pull it off.
So, now you can still use your own custom fonts. No images needed. This technique allows the use of h1, h2 tags to have its copy replaced by a Flash using the desired font.
Google will crawl and index the text content of sifr Flash files. Hence, it’s search engine friendly.
Here is an example of a website that does this. TV Land: (example shown using Firebug).