How to fix an upgraded Firefox profile


Using an older version of Firefox can corrupt bookmarks and browsing history already saved in your existing FireFox profile. To protect your information, create a new profile for this installation of firefox.

I'm an idiot. I ran a new version of Firefox nightly without creating a new profile. When I went to run my regular Firfox, I got this error message: Here's how I fixed it. Close down Firefox Open a terminal and run: firefox --allow-downgrade Let Firefox start up and create a new profile. Then go…

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Change how fast your cursor blinks in Firefox


(Mostly written to prevent me forgetting) In about:config add this setting ui.caretBlinkTime of type integer. Then set the number to how many milliseconds between blinks. 250 is very quick, 500 is about normal. I tend to go for about 400. Set it to 0 if you don't want it to blink at all. Click the…

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Howto: Stop Firefox Forcing Dark Mode on Websites


Firefox dev tools. A pop up informs you that the colour scheme can be toggled.

Here's how to stop Firefox automatically turning on dark-mode for websites. In the address bar, type in about:config and press ⏎ and accept the warning it gives you. Add a new value ui.systemUsesDarkTheme set it to type number and pick one of the following: 0 to tell websites to always use the light theme. 1…

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What's the window size of a background tab?


The Outer window size is zero by zero.

Whenever I open Twitter in a new tab on my phone, the page layout looks weird for a few seconds. It starts out looking like the desktop view and then, after a few seconds, it snaps back to the mobile view. What's causing this? Try opening this link to a window size detector in a…

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Invisible Pink Unicorns - a Firefox emoji rendering bug


The upper image is partially transparent. The lower image is completely opaque.

Here's a curious bug I just discovered in Firefox 67 for Linux. Can you see this unicorn: →🦄 ← What happens if you use CSS to change the opacity of an emoji? Here's a unicorn, with a pink font colour: 🦄 Unicorn Let's wrap that in this scrap of CSS to make it 50% opaque.…

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textarea placeholder bug in Firefox


Screenshot - the text is rendered on a single line

The new Firefox is out! Powered by the ludicrous-speed quantum engine - it really is a marvel to behold. Unfortunately, there's a rather annoying bug in the way it renders placeholder text. Consider the following HTML: <textarea placeholder="In loving memory of Buffy Anne Summers She saved the world A lot..."></textarea> This should render a textarea…

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RTL Bugs


Take a look at the following text, looks normal enough doesn't it? "Harry ‮".draziw a si ‭Potter Now, try to select the text and see what happens. WHAT WITCHCRAFT IS THIS?! If you examine the source code for this page, you'll see that I'm using the Unicode Bi-Directional characters. "Harry &#x202e;".draziw a si &#8237;Potter These…

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Malicious Use of the HTML5 Vibrate API


There is a new API in town! HTML5 will (soon) let you make the user's device vibrate. What fun! Obviously, it's useful for triggering alerts, improved immersivness during gameplay, and all sorts of other fun things like sending Morse Code messages via vibration. At the moment, Chrome (and other Android browsers) ask for permission before…

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Browser Statistics of 10 Downing Street


It's really difficult cutting through the hype to see which browsers one should support when designing a website. There are many different measures of popularity - but many sites are only visited by techies, or only ever visited when at work, or are skewed towards the young or the old. Yesterday morning I asked the…

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