The main reason to optimise site is to load the site as fast as possible. A typical user spends the initial 3 seconds to judge the website and make decision to spend more time on the site.
Its a must that within that time all the content of the website is fully loaded.
So how can we make a proper and well optimised sites. Here are some of my tips.
1) Design focused on user experience
For me a optimisation should start from the core level. So designing a site considering the usability and optimisation is quiet important. I would prefer to sacrifice the look of the site bit better
in favor of proper optimisation. Try to avoid the situation of using image whenever needed.
2) Google Guidelines
Google guidelines provides a lot of tips on design and content, techniques and quality.
Considering the amount of traffic that comes through google, a developer must have a good idea about the guidelines.
3) Use minifying techniques for CSS and Javascript
What does minifying mean? Minifying refers to downsizing the size of the files in order to load it faster. Normally its done by removing the unnecessary white spaces, line breaks etc out of the source
files.
There are number of tools and web services in the internet that can help to minify the CSS and Javasript files.
4) Optimise Images
Image optimisation is quiet essentail part of site optimisation. Normally images are the part of the page that takes more time to load and hence properly optimising images results to better load the
site.
In case where images with low resolution works, then its better idea to go with it. Normally the higher the quality of the image the larger file size it have, so choosing the resolution that works
better for the site is good idea rather than blindly going for the quality.
5) Use CSS Sprite
CSS sprite is a must for site optimisation. It does 2 things that helps in loading site faster.
Firstly by comnbining all images together, it decrease the file size and hence the site has to load smaller chunck of data.
Secondly, by combining all images together it reduces the number of requests that server had to make during the page reload.
6) Use CSS3
This might be bit wierd. But using CSS3 avoids using more images. The latest CSS3 have features like border radius, gradient, text shadows, box shadows, animations and even more.
But then a question arises, IE having a greater market share. But keep in mind that IE's market is gradually decreasing and with the release of IE10 its a good news for the developers as it supports
more CSS3 features. IE9 currently supports some CSS3 features.
But don't forget to use the fallback for the older version of IE [7 and 8].
As a wordpress developer, for me optimising site is as important as developing website itself. In case if you want to learn some technique you might be interested in reading WRITING SEO FRIENDLY HTML.