We've reached the end of our tether here trying to overcome a nasty and intermittent FOUC in Firefox 3.5.x+ for a new release we're working on.
We've tried:
Disabling Javascript in FF
Using Quirks mode rendering by removing the DOCTYPE
Moving from #import for additional CSS to <link>
Switching concatenation on and off
Removing CSS files from the concat, one at a time
Switching the local cache off in Firefox
etc
Our previous release never exhibited any FOUC issues, so it's something we've done to this release. Changes we've made so far include:
Using Base64 encoded images over Data URIs for all decorative imagery, served via CSS.
Separating 'framework'-related CSS files from page-specific CSS and bundling them as two separate CSS files
To recreate the problem... use Firefox 3.5.x or 3.6.x, then:
Head on over to: http://my.publisher-subdomain.env.yola.net/
Login with username: 'stack#yola.com' and password: 'stackoverflow'
Once logged-in, you should be at http://my.publisher-subdomain.env.yola.net/sites/
Click the Account link in the main nav.
The Account page should load, and you should see a FOUC. If the FOUC does not occur, clear your cache and reload the page.
Your help would be greatly appreciated! :)
UPDATE:
The dev environment is still exhibiting the FOUC, but only if FireFox is running low on memory or has a lot of extensions installed. Latency and rendering speed definitely affect the visibility of this FOUC.
Although this is a very old question, I found it when I was searching for a solution to the same problem. So, I wanted to post the solution for future reference. I just needed to move the reference to my CSS files above the references to external Javascript that needed to be in my header.
I can be wrong, but this could be a concurrent connections issue. According to my Firebug's "Net" tab
the HTML page simply takes a lot of time to load - maybe also because it is on a development server? - and the style sheet gets loaded after the HTML page.
I can't claim to entirely understand what's happening here, but I would try putting the style sheet onto a different domain as a first measure. That should make Firefox establish a connection straight away.
It would probably also be a good idea to go back to normal images instead of data: URIs - that would reduce the size of the style sheet, and data: URIs won't work at all in IE < 8.
Related
I'm having a problem with a site that I just made live - I had to correct some CSS issues related to the background and some image placements. Everything of course looks great in VS Code. I open it in Chrome and Firefox and they look completely different - and wrong. Developer tools showed they were using the old CSS stylesheet (which was originally loaded, then replaced). If I open an incognito window, all is perfect. Any reason this would be? I'm new to this (changing careers) so I appreciate your insight!
This is most probably because the css file is cached in your browser. To fix this problem, you can use cache buster in the URL. For ex, your CSS URL is
https://www.abc.xyz/static/css/core.css
So, whenever you make changes in the CSS file, change the URL to this
https://www.abc.xyz/static/css/core.css?version=1.0.1
?version=1.0.1 changes the file URL and hence it is not loaded from cache. Just change the version number when you make the changes to the file so the URL is new again
Not sure how to really categorize this question, but on this page, the file http://d1el287zd12c0j.cloudfront.net/assets/hitgrid-0a8239a14fba0de87431c06cd75774f3.css seems to be completely ignored by browsers. It appears to load successfully and no different than any other css file on the page, but the styles in it are simply not applied to the page.
The content-type, encoding and everything appears to be working as expected. Roughly the same content "applies" fine on my local installation of the app.
I'm at a loss as to what's going on here.
I just check it out and everything went right.
Try to make the filename shorter in the CDN. Large names tend to make error in some way or maybe check if no other stylesheet is interfering with the styles
If that didn't work, answer these questions and Ill try to git it a try again
Which OS are you using?
2. Are you using wordpress?
I've been using Google PageSpeed insights to try and improve my site's performance, and so far it's proven extremely successful. Things like deferring scripts worked beautifully, since I already had an in-house version of jQuery's .ready() to defer scripts until the page had loaded fully, all I had to do was inline that particular function and move the full scripts to the end of the page. That worked great.
But now I find myself glaring at the one remaining yellow dot on the checklist: "Eliminate render-blocking CSS in above-the-fold content".
The way my CSS is set up is to have one global _.css file containing styles that apply to the page structure in general, or are used in more than one or two places across the site. Most pages then have an associated CSS file (for instance, party.php has party.css) containing styles specific to that particular page. All CSS files are cached indefinitely, as I append /t=FILEMTIME to filenames (and later remove them with .htaccess) in order to guarantee that files are updated when they are changed.
So anyway, Google recommends inlining critical styles needed for above-the-fold content. Trouble is... well, take a look at this screenshot: http://prntscr.com/1qt49e
As you can see... ALL of the content is above-the-fold! People hate scrolling, especially on a game that involves loading many pages. So I designed the site to fit on one screen (assuming a good enough resolution). So that means... ALL of the styles apply to above-the-fold content! So... is there any solution? Or am I stuck with that yellow mark on an otherwise near-perfect score?
A related question has been asked before: What is “above-the-fold content” in Google Pagespeed?
Firstly you have to notice that this is all about 'mobile pages'.
So when I interpreted your question and screenshot correctly, then this is not for your site!
On the contrary - doing some of the things advised by Google in their guidelines will things make worse than better for 'normal' websites.
And not everything that comes from Google is the "holy grail" just because it comes from Google. And they themselves are not a good role model if you have a look at their HTML markup.
The best advice I could give you is:
Set width and height on replaced elements in your CSS, so that the browser can layout the elements and doesn't have to wait for the replaced content!
Additionally why do you use different CSS files, rather than just one?
The additional request is worse than the small amount of data volume. And after the first request the CSS file is cached anyway.
The things one should always take care of are:
reduce the number of requests as much as possible
keep your overall page weight as low as possible
And don't puzzle your brain about how to get 100% of Google's PageSpeed Insights tool ...! ;-)
Addition 1: Here is the page on which Google shows us, what they recommend for Optimize CSS Delivery.
As said before, I don't think that this is neither realistic nor that it makes sense for a "normal" website! Because mainly when you have a responsive web design it is most certain that you use media queries and other layout styles. So if you are not gonna load your CSS first and in a blocking manner you'll get a FOUT (Flash Of Unstyled Text). I really do not believe that this is "better" than at least some more milliseconds to render the page!
Imho Google is starting a new "hype" (when I have a look at all the question about it here on Stackoverflow) ...!
How I got a 99/100 on Google Page Speed (for mobile)
TLDR: Compress and embed your entire css script between your <style></style> tags.
I've been chasing down that elusive 100/100 score for about a week now. Like you, the last remaining item was was eliminating "render-blocking css for above the fold content."
Surely there is an easy solve?? Nope. I tried out Filament group's loadCSS solution. Too much .js for my liking.
What about async attributes for css (like js)? They don't exist.
I was ready to give up. Then it dawned on me. If linking the script was blocking the render, what if I instead embedded my entire css in the head instead. That way there was nothing to block.
It seemed absolutely WRONG to embed 1263 lines of CSS in my style tag. But I gave it a whirl. I compressed it (and prefixed it) first using:
postcss -u autoprefixer --autoprefixer.browsers 'last 2 versions' -u cssnano --cssnano.autoprefixer false *.css -d min/ See the NPM postcss package.
Now it was just one LONG line of space-less css. I plopped the css in <style>your;great-wall-of-china-long;css;here</style> tags on my home page. Then I re-analyzed with page speed insights.
I went from 90/100 to 99/100 on mobile!!!
This goes against everything in me (and probably you). But it SOLVED the problem. I'm just using it on my home page for now and including the compressed css programmatically via a PHP include.
YMMV (your mileage may vary) pending on the length of your css. Google may ding you for too much above the fold content. But don't assume; test!
Notes
I'm only doing this on my home page for now so people get a FAST render on my most important page.
Your css won't get cached. I'm not too worried though. The second they hit another page on my site, the .css will get cached (see Note 1).
Few tips that may help:
I came across this article in CSS optimization yesterday:
CSS profiling for ... optimization
A lot of useful info on CSS and what CSS causes the most performance drains.
I saw the following presentation on jQueryUK on "hidden secrets" in Googe Chrome (Canary) Dev Tools:
DevTools Can do that.
Check out the sections on Time to First Paint, repaints and costly CSS.
Also, if you are using a loader like requireJS you could have a look at one of the CSS loader plugins, called require-CSS, which uses CSSO - a optimzer that also does structural optimization, eg. merging blocks with identical properties. I used it a few times and it can save quite a lot of CSS from case to case.
Off the question:
I second #Enzino in creating a sprite for all the small icons you are loading. The file sizes are so small it does not really warrant a server roundtrip for each icon. Also keep in mind the total number of concurrent http requests are browser can do. So requests for a larger number of small icons are "render-blocking" as well. Although an empty page compare to yours, I like how duckduckgo loads for example.
Please have a look on the following page https://varvy.com/pagespeed/render-blocking-css.html .
This helped me to get rid of "Render Blocking CSS". I used the following code in order to remove "Render Blocking CSS". Now in google page speed insight I am not getting issue related with render blocking css.
<!-- loadCSS -->
<script src="https://cdn.rawgit.com/filamentgroup/loadCSS/6b637fe0/src/cssrelpreload.js"></script>
<script src="https://cdn.rawgit.com/filamentgroup/loadCSS/6b637fe0/src/loadCSS.js"></script>
<script src="https://cdn.rawgit.com/filamentgroup/loadCSS/6b637fe0/src/onloadCSS.js"></script>
<script>
/*!
loadCSS: load a CSS file asynchronously.
*/
function loadCSS(href){
var ss = window.document.createElement('link'),
ref = window.document.getElementsByTagName('head')[0];
ss.rel = 'stylesheet';
ss.href = href;
// temporarily, set media to something non-matching to ensure it'll
// fetch without blocking render
ss.media = 'only x';
ref.parentNode.insertBefore(ss, ref);
setTimeout( function(){
// set media back to `all` so that the stylesheet applies once it loads
ss.media = 'all';
},0);
}
loadCSS('styles.css');
</script>
<noscript>
<!-- Let's not assume anything -->
<link rel="stylesheet" href="styles.css">
</noscript>
I too have struggled with this new pagespeed metric.
Although I have found no practical way to get my score back up to %100 there are a few things I have found helpful.
Combining all css into one file helped a lot. All my sites are back up to %95 - %98.
The only other thing I could think of was to inline all the necessary css (which appears to be most of it - at least for my pages) on the first page to get the sweet high score. Although it may help your speed score this will probably make your page load slower though.
The 2019 optimal solution for this is HTTP/2 Server Push.
You do not need any hacky javascript solutions or inline styles. However, you do need a server that supports HTTP 2.0 (any modern server version will), which itself requires your server to run SSL. However, with Let's Encrypt there's no reason not to be using SSL anyway.
My site https://r.je/ has a 100/100 score for both mobile and desktop.
The reason for these errors is that the browser gets the HTML, then has to wait for the CSS to be downloaded before the page can be rendered. Using HTTP2 you can send both the HTML and the CSS at the same time.
You can use HTTP/2 push by setting the Link header.
Apache example (.htaccess):
Header add Link "</style.css>; as=style; rel=preload, </font.css>; as=style; rel=preload"
For NGINX you can add the header to your location tag in the server configuration:
location = / {
add_header Link "</style.css>; as=style; rel=preload, </font.css>; as=style; rel=preload";
}
With this header set, the browser receives the HTML and CSS at the same time which stops the CSS from blocking rendering.
You will want to tweak it so that the CSS is only sent on the first request, but the Link header is the most complete and least hacky solution to "Eliminate Render Blocking Javascript and CSS"
For a detailed discussion, take a look at my post here: Eliminate Render Blocking CSS using HTTP/2 Push
Consider using a package to automatically generate inline styles from your css files. A good one is Grunt Critical or Critical css for Laravel.
When I make a page, link it to a CSS file, and open it in a browser, it works fine.
But if a make a change and refresh the page again between very short time periods, the change is not reflected. But after sometime, when i refresh the page again, the changes appear.
So, somehow the browser keeps the CSS file cached and expires it after sometime. How to make the browser cache no CSS or HTML file.
It would be better if i can block it on a particular domain.
I'm on Ubuntu, using Chrome and Firefox, trying to prevent browsers from caching CSS files on 'localhost'... How to do it...
Thanks...
Something as simple as this should work:
<link rel="stylesheet" src="/css/screen.css?v={CURRENT_TIMESTAMP}">
Just replace {CURRENT_TIMESTAMP} with the actual timestamp in your server side code. This makes the browser think it's a new file because of the query string and it will be downloaded again. You could also use the actual modification time of the file (filemtime('/path/to/css/screen.css') if you're using PHP) which should prevent unnecessary downloads.
You can open Developer Tools by pressing Ctrl+Shift+J and then you'll find a cog icon in bottom right. When you click on it you should see an option to disable caching.
It would help to know how the website is hosted, as you can configure this in most web servers.
Also, it's a good idea to introduce a cache busting mechanism which would modify the links to the CSS files in question when you change the CSS files' contents. Browsers would then reload the CSS file because the HTML refers to a different URL.
A good example of a cache busting mechanism is the ruby on rails 3.1 asset pipeline which also minifies files and gzips them if the browser supports them:
Rails 3 - Asset Pipeline -- What does it mean to me?
http://2beards.net/2011/11/the-rails-3-asset-pipeline-in-about-5-minutes/
The seemingly-inelegant but rock solid approach is to give the asset a new name, when the content changes. This solves the problem for all your users, not just you:
<link rel="stylesheet" src="/css/screen_034.css">
<link rel="stylesheet" src="/css/screen_035.css">
<link rel="stylesheet" src="/css/screen_036.css">
Or maybe (but it's more of a pain to change in an IDE, and sometimes causes unrelated problems with caching):
<link rel="stylesheet" src="/css/screen.css?pretend_version_number=034">
Nothing else works quite as well in large scale production environments, where millions of copies of an older css file may be sitting in various intermediate or browser caches. Some clients ignore cache control headers, and you don't really want caching subverted anyway, at least not in production.
In development you can press Ctrl+Shift+J (Chrome) and turn off caching.
When I make any changes to my CSS file, the changes are not reflected in the browser. How can I fix this?
The fix is called "hard refresh"
http://en.wikipedia.org/wiki/Wikipedia:Bypass_your_cache
In most Windows and Linux browsers: Hold down Ctrl and press F5.
In Apple Safari:
Hold down ⇧ Shift and click the Reload toolbar button.
In Chrome and Firefox for Mac:
Hold down both ⌘ Cmd+⇧ Shift and press R.
Try opening the style sheet itself (by entering its address into the browser's address bar) and pressing F5. If it still doesn't refresh, your problem lies elsewhere.
If you update a style sheet and want to make sure it gets refreshed in every visitor's cache, a very popular method to do that is to add a version number as a GET parameter. That way, the style sheet gets refreshed when necessary, but not more often than that.
<link rel="stylesheet" type="text/css" href="styles.css?version=51">
A good way to force your CSS to reload is to:
<link href='styles.css?version=1' rel='stylesheet'></link>
And then just increment the version number as you change your CSS. The browser will then obey. I believe Stack Overflow uses this technique.
I always use Ctrl+Shift+F5 out of habit, it should force a full-refresh including by-passing any http proxies you may be going through.
I had this issue. Turns out I completely forgot I had CloudFlare setup on the domain I was live testing on.
CloudFlare caches your JavaScript and CSS. Turned on development mode and BAM!
Do Shift+F5 in Windows. The cache really frustrates in this kind of stuff
This sounds like your browser is caching your css. If you are using Firefox, try loading your page using Shift-Reload.
Having this problem before I found out my own lazy solution (based on other people suggestions). It should be helpful if your <head> contents go through php interpreter.
To force downloading file every time you make changes to it, you could add file byte size of this file after question mark sign at the end.
<link rel="stylesheet" type="text/css" href="styles.css?<?=filesize('styles.css');?>">
EDIT: As suggested in comments, filemtime() is actually a better solution as long as your files have properly updated modify time (I, myself, have experienced such issues in the past, while working with remote files):
<link rel="stylesheet" type="text/css" href="styles.css?<?=filemtime('styles.css');?>">
The Ctrl + F5 solusion didn't work for me in Chrome.
But I found How to Clear Chrome Cache for Specific Website Only (3 Steps):
As the page is loaded, open Chrome Developer Tools (Right-Click > Inspect) or (Menu > More Tools > Developer Tools)
Next, go to the Refresh button in Chrome browser, and Right-Click the Refresh button.
Select "Empty Cache and Hard Refresh".
Since I found this thread having the same problem, 10 YEARS later, I'll add my own solution too. I use PHP most of the time, and rather than requiring the user to press unusual buttons to refresh the page, or myself to remember to bump a version number embedded in a link, I used the filemtime() function to get the modification time of the css file (as a unix timestamp), and then use THAT number as the parameter.
$FILE_TIME = filemtime("main.css");
$CSS_LINK = "main.css?version=$FILE_TIME";
While results in a URL like:
http://example.com/blah/main.css?version=1602937140
This entirely disables caching, since every time the page is refreshed, it will believe it needs to grab the CSS file again, changed or not... but that's far less frustrating than forgetting to manually update this trick and wasting time wondering why it isn't right. You can always remove it from a production server.
If you are using plain HTML, you could probably engineer a javascript wrapper or some such, but that's probably more trouble than it's worth.
Have you tried renaming the new version of your CSS to CSSv2.css and then directing your page to use that? If that solves the stale-file issue, then you're just experiencing non-refreshing files. If not, you've got bigger issues.
If you're using ASP.NET web forms, make sure that you are using the right theme:
I just spent about an hour trying to solve this!
Is this a local custom CSS file? Is this your website? Maybe you should clear your cache.
Also the last CSS declaration takes precedence.
I faced the same problem. Renaming the file worked for me.
The reason this occurs is because the file is stored in the "cache" of the browser – so there is no need for the browser to request the sheet again. This occurs for most files that your HTML links to – whether they're CDNs or on your server, for example, a stylesheet. A hard refresh will reload the page and send new GET requests to the server (and to external b if needed).
You can also empty the caches in most browsers with the following keyboard shortcuts.
Safari: Cmd+Alt+e
Chrome and Edge: Shift+Cmd+Delete (Mac) and Ctrl+Shift+Del (Windows)