I've taken a lot from Webmasterworld - my questions are usually answered and everyone has been very helpful. Looking back though, I don't think I've actually inputted that much myself.. so am going to make an effort to share some of my research..
If you sell anything on your website page loading is hugely important. Although broadband has become faster, people's expectations have matched this, and their patience has diminished. Having a faster loading page can increase conversions, leave your users more staisfied, and also affect your adwords positions (potentially also your organic rankings)
In my quest to get the fastest loading pages I've discovered the following:
a) Server Location
Hugely important! If your server is in the US but your customers are in the UK then everytime a page is called then there has to be a physical connection to the server... under the Atlantic, through countless routers.. It's not uncommon for there to be around 20-30 hops.. this increases your page loading time and because it goes through so many routers there are more potential points of failure where you can be timed out. Remember, you're only as fast as your slowest route as well.
Have a look at your trace route and see how you're doing. There are also some really good other free tools like Visual route which will trace the path to your server.
b) Server side
- Ensure your CPU is working properly! If you're having lots of traffic, is it working optimally, or is it good enough to handle the volume?
- If you've got a DB, this is a potential area of massive problems. I'm not going too much into that (others will know uch more!), but investigate and see if it's working ok
- Connection speed / bandwidth to server. What is your host providing. Is it a fast line? How does it react under pressure of high traffic levels. If you can, load test..
c) Look at Y Slow, another free tool to see where you're good and where you can improve to get faster loading.
d) Reduce number of objects called - each time an object is called adds time to the page load! Try and condense images etc, put them together, and equally, put Javacript into one external file.
f) CSS - not tables! CSS makes everything if implemented well
g) Talking about CSS, cut out the rubbish in it and cut out the white spaces.. there's tools on the web which will optimise your CSS for free
h) Images - optimise them, crunch them to death, and try not to use too many!
i) If you're using PHP look at e-Accelarator, it caches and optimises your PHP for you. A few more milli-seconds gained..
j) Compress your output - something like Mod_deflate will Compress output from server before it is sent to client (compresses HTML only really – not images or anything else)
I hope this gives people an initial idea on what to do to get the most out of their pages / sites... There is of course a lot more, and I'm still trying to find things out!