On average, roughly 45% of a web page's weight is made up of images. Considering the size of that number, optimized images are the best way to speed up a website. A study for Amazon.com has concluded that each 100ms slower the page loads, equates to a 1% drop in sales. It's no wonder they go to great lengths to expedite page weight, and why you should too.

Up until the last couple of weeks, I didn't have a great understanding or appreciation for image optimization. I, like many others in our field, left the dirty work to Photoshop and assumed it would produce the lightest possible images.

Learning the basics about image formats, what works best for certain applications and what tools are out there to help, is something all web designers and front-end code monkeys need to master. I've put together a collection of best-practices and resources over the last couple of weeks that should be helpful:

Highlights

PNG gets a bad wrap.
PNG is not only useful for alpha-transparency, but in nearly every case is better quality and lighter weight than a 256-color GIF. For more on this, check out the Image Optimization series linked up below.

Make use of CSS sprites.
Sprites are an advanced CSS technique, but can be HUGE in creating lightweight websites and applications. Read this Smashing Magazine feature for a great round-up of CSS sprite resources.

Adobe CS4 does not have it mastered.
Optimization in Adobe Creative Suite 4 is inconsistent. Photoshop does an average job optimizing images for web. Fireworks does a much better job, with JPEGs especially. Neither do particularly well with PNGs, and require outside tools for best results. The Adobe team says that the Fireworks web optimization features are coming to Photoshop in the next release, so we'll see.

Additional Reading

Yahoo! and their people have led the way when it comes to prioritizing website performance. Stoyan Stefanov (member of the Yslow team) has written a very educational 5-part series about image optimization that is a must-read:

1. The Importance of Images
2. Selecting the Right File Format
3. Four Steps to File Size Reduction
4. Progressive JPEG ... Hot or Not?
5. AlphaImageLoader

Tools

Smush.it
Developed by the aforementioned team at Yahoo!, this website will take all the images on a given page, optimize them, and ZIP them up in a tidy little folder for you to download. It also shows you the measurable size improvements made on each image. It's a phenomenal tool we will not ever launch a project without in the future.

PNGthing
This is a very handy little Mac application for optimizing PNGs, since Creative Suite is not there yet. Simply drag an individual image or folder to the application icon, and it will optimize all PNGs for you within a matter of seconds, showing how much you saved in a little Growl notification. I love it.

The 5-part series from above mentions a bunch of other, more geeky command-line tools for optimizing images, but the two above tools work best for my needs. Happy optimizing!

Imagine for a moment that you are engaged to be married. One very important decision you have to make is choosing a photographer for the wedding and reception. Photographers can easily cost $2,000 and up, so you want to be sure about your choice.

You are having a tough time making a decision, so you invite five photographers to participate in your wedding. There is only one caveat: once the wedding is over, you will review the all photographs, and choose the one photographer you like best and only pay that person. The other four get a friendly handshake and nothing more for their hard work.

This is the concept behind what people in the design world refer to as "spec work". It's been quite a hot topic as of late. Entire websites (this one too) are now dedicated to helping companies find designers willing to do spec work, and basically compete for the right to work with a client on their project. We have gotten inquiries about doing spec work at least twice already this year, so I feel like it is important to explain why we don't participate.

The Process Gets Shorted

One of the criteria that must be met before we take on a project is answering YES to the following question: "Can we do really great work?" Our very best design work is the result of seamless collaboration with the client, extensive research and careful planning before ever getting started on the visual design. With spec work, this part of the process is often cut short or ignored all together.

By choosing a design created on spec, it gives too much weight to the visual side, instead of what will perform best with customers or help grow your business. The visual part of a site is only one piece of the puzzle, but with spec it is often the only piece of the puzzle considered by the client upfront.

We enjoy the process of creating a user-friendly, effective website; but that process takes a lot of time and effort. It's simply not feasible to do it all for free, with no guarantees of getting paid for it eventually.

When Spec Does Make Sense

Whether spec makes sense for you as a client is all about what you hope to achieve with the design. If one or more of the following characteristics describe you, it's possible that it will be a good fit:

• You can accept that the initial work will not be as polished or thorough
• You don't really have a good idea of what you want "until you see it", and need to see styles and variety that is all over the board
• Your budget is limited, and expectations are not incredibly high
• You have no problem working with someone that's less experienced, but eager to learn

Decide What Works for You

I personally think it's wrong to expect any professional to perform 10-25 hours of service free of charge without any guarantees. But plenty of creatives are totally okay with it! If you are a designer, and use spec work as an opportunity to prove yourself and get better, then make the most of it.

No matter what side of the fence you are on, it's important to respect those on the other side. Some of that has been lost in all of this banter across the web. We spend a ton of time on all our projects and really dedicate to the process, so spec does not make financial sense for us or the clients we work with. However, for those that can make it work and are proud of the results, more power to you!