Version 23

Speed optimisation

being frendly to dial-up users

Created by: dspt, Last modification: 27 Apr 2006 (19:25 UTC) by dspt


so the bw has the same issues as any big modular CMS - its' pages are heavy. Let's use not-perfect-but-nevertheless-usefull online speed report at webpageanalyzer
Main Wiki Page of bw gets analyzed
At the time of writing this page, the statistics were:
Total HTTP Requests:31
Total Size:103767 bytes

Object typeSize (bytes)
HTML Images:24920
CSS Images:13273
Total Images:38193

Download Times
Connection Rate Download Time
56K20.68 seconds
ISDN 128K6.33 seconds

Jakob Nielsen is positive that we should achieve sub-8 seconds load time for the users to like navigating our site. Another reason for speed optimisation is reducing the load for sites with heavy traffic.
This is obviously a rather impossible task to scale down the 120k page (20k of css is omitted by the analysis) to 30k, necessary for sub-8 load time, but we might want to get closer to that usability ideal. (side note: at that moment BW was using AJAX for some packages — 45k!!)
So what should we take into consideration, when theming and tweaking the bw?
The basics are simple:
  1. eliminate extra size (obvious)
  2. eliminate extra HTTP requests (less obvious. reading: Modem connections (56Kbps or less) are corrected by a packet loss factor of 0.7. All download times include delays due to round-trip latency with an average of 0.2 seconds per object. With 31 total objects for this page, that computes to a total lag time due to latency of 6.2 seconds. we are loosing more then 6 seconds just for http requests, so there's no chance for sub8 response :( )

mind HTTP requests: combine and pack

in short "the less requests the better", so before optimyzing file size think how to reduce quantity of files per page.
  1. Think twice before you start "slicing" into small pieces your images and backgrounds in some Adobe ImageReady. This technique is an offspring of table-based layouts — when bw has div-based layout at the moment. IMHO with div-based layout you might get better results having 3 big background images instead of 30 small ones.
  2. Also, some of the images CAN be eliminated without any damage to the style. There's a nice CSS trick for rollover images (If using graphic rollover at all): the rollover images are stacked in single background file vertically, and on :hover the vertical position of background is changed in CSS. The same can be done with very small images, like icons and signs of external link etc. The trick is that it doesn't give any boost in load time if the file is smaller then 1160 bytes - it's still single TCP-IP packet. So we can combine two small graphic files if their total is still less in size then 1k. This way we cut off 1 packet and 1 http request. (At this point, reading about how much effort is needed to save 0.2 seconds, all readers are confident I'm crazy and need psychiatric attention %/ )
  3. Combine javascript and CSS files: put all external css into one file - less files means less http requests. (It seems like all CSS is already in 1 file for Jill theme, but it's not, because you have package specific CSS, like CSS for fisheye div-based galeries and PHPBB CSS. There're also portions of package specific css declarations in main file, that are worth deleting if you don't use that package: stikies etc.) Eliminate redundant markup before uploading to the server, but leave read-frendly version locally for editing. In general, BW uses very complex css for styling. As a web-designer, I like this approach. But despite my optimisation efforts the css in my installation is still over 15k. At the moment reducing the size of CSS can only ocure with introduction of new theme and rethinking majority of the templates. Ready to jump in? RethinkingTemplates If you have any suggestions, please add to this text.
  4. Then search your bw installation for majorly used javascript files: put them together, then eliminate redundant markup and pack. Currently /xing has already implemented Dean's packer in HEAD, but it omits the first step, which costs about 10-20% size. Also, in distro the used js is parted into different files, because of BW modular structure: some .js files only required by specific packages. But in real installation it's different: you know what packages you are going to use, so you CAN combine all used .js in 1 file. Js in my installation (1.3) is less then 8k. It's only 3k and 3 http requests smaller then original BW .js set, but I'm sorta proud of it :)

Side note: CSS and javascript are cached, so they are loaded once in a while, but they do load the first time, which is the most important for the visitor: if he chooses to stay and wait for the site to load or he closes the browser tab and forgets about your site existence. Once again, Jakob Nielsen says most visitors will close page if they will not get response in 8 seconds. This is disputable, though, as this findings are sort of outdated. Also, the amount of dial-up users in North America and EU is decreasing, so speed optimisation might be not so important for many sites.

Beware of the IE6

There are browsers, and there's IE. You might want to use nice modern techniques to style your site, but IE renders them wrongly or differently, so you might wind up in the situation when you have a nice styling + enormous tail of CSS hacks, javascripts etc., forcing your style to look as intended in Explorer.
  • transparent png files are nice, but they don't work with IE6, and require various fixes to be displayed correctly. Thus, by creating nice design pattern with the png, we add unnecessary js fixes: minimum +2 files equals in extra size and extra http requests
  • we should also mention Box model, CSS2 and CSS3 selectors, non-collapsing or unexpected margins etc. You either fix them with CSS hacks (adding extra bites to your CSS sheet) or Javascript like Dean's IE7 . I recommend conditional comments, CSS hacks or avoiding usage of such elements when possible. consult my favourite css resource for knowledge and help.
read more at theme compliance with MSIE

image optimisation

My offer is to postpone using .png until IE6 is history. And if we are not using alpha transparency, why use it: it usually optimises for size worse then .gif. If you really want to use it, use it together with PNGCRUSH or other similar packer.
As for regular .gif or .jpg, I'll not waste my time explaining. If you don't know it, quit webmastering.

semantic layout

Current Jill theme already has it: first in code comes bitmain, only then columns. Hurray for xing! If you are creating custom theme, don't forget about this. It's not exactly conventional speed optimisation, but it's important.

other compression

BW have function to activate gzip. Use it. Also, use { strip} tags in smarty templates.
One more thing: if browser loads DOM (more specifically receives all necessary dimensions of all the objects), it shows the page before images are loaded. Always set their height, width (and alt), the page will be rendered faster. Same for tables. The same impact on browser seems to be caused by the
tag. The code before rule is rendered before the rest is loaded.


decided to pass mainpages of other CMSes through analyser. Results:
Link to page analyzedTotal HTTP Requests Total Size load time on 56k modemremarks
bitweaver3159368 bytes11.83 seconds20k css file is not calculated
TikiWiki21189316 bytes38.13 secondsquite a lot of everything
Joomla60200149 bytes40.29 secondsover100k http images!
Drupal5185049 bytes17.95 seconds0(ZERO!) javascript
Xoops30131660 bytes26.24 secondssome broken links
Xaraya49191770 bytes40.82 seconds60k CSS in 14 files!
e10773238522 bytes47.94 seconds170k images! (which also means the actual frame is rather slick)
mediawiki2984136 bytes18.37 seconds30kb css in 8 files - seems unnecessary for such a basic layout

Please add other contenders to this table
with >30 http requests and about 80k weight we are looking good :)
Page History
31 May 2010 (12:05 UTC)
While most othe content here is incredibly old, I updated WSO's result as a start.
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