1. The document discusses common issues with fonts on the web, such as fonts appearing differently across browsers and operating systems. This is due to differences in how fonts are rendered in Windows, Mac, and other platforms.
2. It recommends always using web-safe fonts and font stacks to account for variability. Font stacks allow the browser to substitute alternate fonts if the primary font is unavailable. Common web-safe fonts like Arial, Verdana, and Georgia are widely available.
3. Rendering issues can occur because web design is viewed on many devices, unlike print where quality is consistent. Accounting for variability in operating systems and browsers is important for web fonts.