Gzipping components is now pervasive, but it’s such an easy, big win that you should confirm your web server is sending compressed files. For scripts and CSS the savings are huge; less so for images, which should already be optimized.
Depending on the number of components on your site, the sizes of those components, and the geographic distribution of your users, it may be a big performance advantage to use a Content Delivery Network. CDNs serve data physically closer to your users, and can make sites much faster.
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.