This document discusses various techniques for optimizing website performance, including: reducing page generation time through caching and opcode caching; minimizing round-trip times by leveraging browser caching, combining files, and parallel downloads; decreasing response sizes by gzipping files, image optimization, and using a CDN; and improving rendering through CSS/JS placement and preloading. Tools mentioned for analyzing performance include XDebug, WinCacheGrind, Page Speed, and YSlow.