gzipping assets is one of the simplest and most effective things you can do to make your web site faster.
For text files we are sending over networks, gzip is a big win and a no-brainer. However, images and other binary files should already be aggressively compressed, and you usually won’t benefit from gzipping them. In fact, binary files can increase a tiny bit in size because of added gzip headers. See this post for more details.
CDNs serve data physically closer to your users, and can make web sites much faster. It’s one of the most important considerations for performance.
A redirect might make a URL such as http://treefrogs.com into http://www.treefrogs.com or http://treefrogs.com/ (simply adding the forward slash). Redirects slow down web sites, so remove any redirects that are not required.
iOS does not support Flash. If you want your site to work on mobile devices, replace Flash with HTML5 or at least include an HTML5 fallback to support that ever-growing group of users.
It’s true that the average web site’s size has surpassed 1MB. But it is also true that most web sites are excruciatingly slow and unusable on mobile — mobile being the future of web browsing.
Be among the best. Keep your pages smaller than 500K.
IDs must be unique to an HTML document.
They are harmless, but if you’d like to reduce and clean up your code a bit, you can remove XHTML close tags (” />”) from elements.