First of all, why do we need to reduce it? There are two main reasons for reducing the bandwidth waste to the utmost minimum. First, the visitors convenience - some users are on dial up, some are impatient, and long loading sites often result in connection timeout, or the visitor just gives up and closes the browser. As a result you lose traffic, clients, and if your site is ads supported - money.

The second reason is that using more bandwidth that you were provided with will either result in your site going offline until the end of the month or will force you to upgrade to a bigger, more expensive hosting plan. As my website grew up, I ended up upgrading many times just to avoid downtime, and in the end been too lazy to optimize the site for fast loading hurts the pocket.

So, what do we do to economize the data transfer for everyone’s benefit?

1. Clean XHTML code, tableless, based on CSS layout will save the pages loading, as crap and messed up code effects your browser’s loading time.
2. Optimize the images you are using. You can do it both online using images optimization tool, or in Photoshop / ImageReady on your computer. In most cases you can halve your .jpg’s weight without affecting the quality.
3. Avoid using big images, if you want to display wallpapers, tutorial’s screenshots, etc, make clickable thumbnails, which will lead to the full sized image. You will be surprised, but most visitors do not view the big resolution images, so wasting so much data transfer upon every hit is unjustified.
4. If you are really tight on bandwidth, you may want avoid employing flash as template of header elements. These files eat up tons of bandwidth, and if you do not have some mind blowing design to show off, switching to elegant and sleek, aka web 2.0 style could be a very practical solution.
5. Movies, music and other media files placed on the site could be crucial for your bandwidth usage. I’d suggest to store just files on free hosts and hotlink to them on your website, to prevent from the entire site from going down in case your downloads suddenly got too popular.
6. Disable hotlinking (i.e. direct requests of the file through your host). Free servers normally disable it automatically, but if you are paying for your hosting, go to cPanel and disallow hotlinking. You might be amazed amazed how dramatically your BW usage will decrease. Well, when I blocked hotlinking from my hosting service once, I was astounded.
7. Last but not least… This is a very tiny and probably unworthy advice as most webmasters use CMS nowadays, but just do you know - html pages are about 2 time smaller than php pages, let alone php are normally constructed from a few files, each of which is 20+ bytes, unlike clean html page that of codded wisely, wouldn’t exceed 9-10 bytes. If your site doesn’t require constant and frequent updates, yet have 5k + visitors daily, working with a “lighter” coding language, especially if you have little downloads, images, etc, could help.

I hope this pours some more light into this whole bandwidth mystery. Remember that in order to calculate your website’s needs you need to know how heavy is your site and how many visitors are viewing it daily. More on this in my “How much bandwidth will my site use?” article.