&gt; And the new stuff, especially Firefox, is coming full circle in how friggin&#x27; slow they run to serve the lowest common denominator of web pages.<p>It should be easy to find performance numbers showing how Firefox 42 renders old, pre-CSS pages slower than, say, Netscape 4, then.<p>Netscape 4 didn&#x27;t have a JIT, didn&#x27;t use hardware accelerated layers, trapped into kernel mode for GDI calls, didn&#x27;t use accelerated SIMD for painting, and didn&#x27;t have HTTP 2. It barely had any optimizations for dynamic restyling, so tons of stuff would get reflowed when it didn&#x27;t have to. This is just the tip of the iceberg.<p>Browsers have gotten more complex, but the complexity is often in the service of making things <i>faster</i>.