“This feature will change everything” might be a bit of an exaggeration, but it, surely, will change a lot, both in #CSS and #SVG. In this post, I’ll report on what is happening right now with it,...

An email from Eric Meyer prompted me to revisit my 2014 argument against CSS variables: what I missed, how I use them now, and why fallbacks still matter.

Container style queries let a component restyle itself from the value of a custom property, and since May 2026 they work in every major browser.

Custom media queries let you name and reuse media queries the way custom properties do for values. Here’s a set of drop-in @custom-media presets for input mechanisms, breakpoints, and true HDR, plus...

Wiring HTML attributes into CSS with advanced typed attr(), and letting container style queries pass that state down to child components.

Edit (2026.08.24): Got feedback from the Web Components Community Group that I was mixing up inheritance, specificity, and the cascade and that * might be a better selector than :defined. I agree with both of those perspectives and I’ve updated this post.

The default might not be what you expect, and it has a big impact on your styles.

The default might not be what you expect, and it has a big impact on your styles.

For custom properties (aka CSS variables) we got into the habit of declaring variables in a rule with a <code>:root</code> selector. Yet unless you’re working in an environment in which style sheets s...

I've tried to create individual install logfiles by modifying Collection.xml. You can see the use of  variables in the CustomProperties section but when I use environment variables in the logging section I just get filenames with the environment variables in the filename as shown below. <LoggingSettings> <Logging>true</Logging> <Path>\\\starling\logs\\[USERNAME]_[COMPUTERNAME]_2026_ACAD.log</Path> </LoggingSettings> <LoggingSettings> <Logging>true</Logging> <Path>\\\starling\logs\%USERNAME%_%COMPUTERNAME%_2026_ACAD.log</Path> </LoggingSettings> <Bundles> <Bundle SeqNo="0"> <Applications> <Application> <CustomProperties> <Property name="SUPPORT_CONTENT_ROOT" value="[ROAMINGUSERFILESFOLDER]"/> </CustomProperties> </Application> </Applications> </Bundle> </Bundles>

Add CustomProperties to a VM Deployment after the Virtual Machine is created.

The `!important` part doesn't become part of the value, the whole declaration is treated as !important;

TPAC 2025 just ended, and I am positively tired. Attending it remotely, my sleep schedule is chaotic right now. I have many ideas for CSS-related posts in my list of ideas for November, but almost all of them require at least some amount of research and crafting demos. Well! I found one note that…

SVG is one of those web technologies that’s both elegant and, at times, infuriating. In this article, pioneering author and web designer Andy Clarke explains his technique for animating SVG elements that are hidden in the Shadow DOM.