Since you give no site or page to verify what your asking about no one is going to know where to start figuring what is going on.

BillM said

Fix the [...] yellow-bar warnings, once and for all. "A web page is slowing down your browser" is NOT a helpful diagnostic; but we've been seeing it for years now.

Please replace it with something that will lead customers to figure out how to solve it. For starters, report WHAT site is triggering the yellow-bars.

Fix? We are FF users, volunteering here to help in this Community Forum. The Mozilla Tech/Coders are not here. You can click on Help > Submit Feedback to Mozilla about fixes and features. Bugs to Bugzilla.
The 'Yellow' Slow-Down Bar Warning is two or three-fold related, I'd guess.
It's a combo of how slow a page is loading and how fast (or slow) does FF work on your system. The third, being if slow Cable InterNet speed plays a part. (Slow DSL service can be a real headache, due to telephone line noise and binary parts getting corrupted and having to re-download again and again until you receive it 'clean'. Forget about Dial-Up Service.)
I'd say the very page you're on in a particular Tab is the 'guilty' party of the slow loading, be it the front page or some other sub-page of a Website.
Some sites or parts of sites are heavily coded with Scripting and Ads. Old, slower computers of years past can suffer, as in my 2010 system I'm on now. I've made changes at my end to keep Quantum working fairly decent.
I regularly 'Quit' FF and resume my Session about every 3 to 5 days (depending on how many Tabs load if I open a lot of sites/pages) to gain back Memory to keep things running smoothly. And, every so often, ReBoot my computer.
It's now rare for me to see Yellow Bar Warnings in Quantum vs the older FF engine along with the adjustments and hard drive cleanup. (Try to have 25% or more of Free Drive Space Remaining. If it's a whole lot less this this, then you may have a severe performance hit.)
You can ignore the Warning and see if the page finally loads. Even if it does load, I bet your performance is down (like it was for me). I'd guess this tells me you need to re-evaluate what your FF and computer setups are and try to help each one for better performance (and less Yellow Bar Warnings).
Are you game?

~Pj

I've -never- seen a yellow-bar message that *successfully* loads the page Since the text has phrasing to the effect of "A web page is impacting your browser," I've always figured that identifying the offending web page would help. I get these once a day or so, but have been unable to associate them with any URL. Surely whoever "owns the code" that includes the message-text could make some headway with solving this.

Do you have anything switched off in your browser that might affect the web page, or use an ad blocker on a page that uses ads, if the page is 'waiting' for such things to load, and you have diassallowed it, it may be waiting to render items and can't, and this makes a page appear unresponsive, its not the browser that causes slow loading pages, it can only render what its sent over the connection.

FredSheehan said

Do you have anything switched off in your browser that might affect the web page...?

I still say it's the NoScript Extension he's using. I had way too many problems using that Extension.

~Pj

I've been using NoScript for MANY years ... it is certainly not geared to newbies.

I actually wanted to file bugs on these issues in bugzilla... unfortunately I haven't used it in months, so I've misplaced my login.

What's the best path to resolve *that*? Create a whole new one?

The yellow-bar MESSAGE TEXT is USELESS. It is IMPOSSIBLE to tell if the page you're coming FROM is the problem (as the browser attempts to unload the now-currently-active image) ... or if the problem's the page you're moving TO.

As a TEN-YEAR Firefox user, I'm thoroughly fed up that no one in the organization is taking responsibility for these DEFECTS that have been present for YEARS. Obviously volunteer developers don't care enough to FIX hard-to-find problems that have existed for years.

The LEAST Mozilla should do is FIX the yellow-bar message *text* (to provide a diagnostic clue *identifying* all source-pages that are being painted, whenever this yellow-bar message appears)... which is several times a week, for me.

I will make one last try via bugzilla ...

And obviously no one cares to fix the annoying, distracting ANIMATIONS that Firefox ADDS to the page image (commonly on 'tabs') ... which do not appear with other browsers... and which STEAL CPU CYCLES and PRODUCTIVITY from Firefox users, especially those of us on lower-end CPUs.

Are you able to post any system specs on this forum?

Based on the fact that you referenced the Celeron 900, a discontinued single-core legacy processor that is turning 10 years old soon, it sounds like you may simply be running slow hardware that's not capable of running modern software with high performance.

Wesley Branton said

Based on the fact that you referenced the Celeron 900, a discontinued single-core legacy processor that is turning 10 years old soon, it sounds like you may simply be running slow hardware that's not capable of running modern software with high performance.

I tried telling Bill this. He's blaming modern software instead of the old, memory-choked system he has. My computer is over 8 years old. I see the Yellow Bar notice briefly here and there, but not as as much since making adjustments and getting rid of NoScript.
Once I cut-down my 822 Tabs in this browser window down to something more reasonable, FF should run even better, I hope, on my system.

~Pj

(I never have more than 5 tabs open... so for me, that's a red herring.)

I've seen no verified claims that the yellow bars are related to NoScript (although that's remotely possible).

"Getting rid of NoScript" opens a privacy/security hole - that's why NoScript exists... to limit the ability of active code from other pages to independently change data on a displayed page, during a session.

The sites that trigger the yellow bar aren't predictable, but Firefox is the ONLY browser that produces the yellow-bar warnings AFAIK, so it counts as a defect to end-users.

I am inferring (no proof yet) that it's Javascript code embedded in the suspect pages that triggers the yellow bars. Good news: the frequency of occurrence has dropped substantially... Thank You to any/everyone!

The Firefox developers won't remove the yellow warning bar because it's an important warning message. If you are seeing this message often, that's not normal and something is likely slowing down Firefox. The average user never (or rarely) sees this warning message.

The message is telling you that something on that website is slowing down Firefox. That generally means that maybe there is a script running on that website that is constantly running and using up too many resources. But there can be other causes as well.

It could be that Firefox is just running slow on your system. That can be caused by various different factors such as, the extensions you have installed on Firefox, the other software installed on your computer, the anti-virus software you are running on your computer, the age of you computer, whether or not you are running the latest Windows updates, how many tabs you are running, what websites you are visiting, etc.

If Firefox is running slow on your system, here are some documents that you can read to improve the performance of Firefox:

• Quick fixes if your Firefox slows down
• Firefox uses too much memory or CPU resources - How to fix
• Firefox uses too much memory or CPU resources - How to fix

But the bottom line is that this yellow warning message you are getting isn't just some pointless message. It's actually trying to tell you something.

BillM said

... "Getting rid of NoScript" opens a privacy/security hole - that's why NoScript exists... to limit the ability of active code from other pages to independently change data on a displayed page, during a session. ...

The internet has changed a lot in 10 years. It used to be that NoScript would "see" a web page loading data from (maybe a max of) 10 different domains to load a "common webpage"; now-a-days it's common to see data coming from 25 or more different domains. Many of those different domains are "social networking" websites. (And if you don't want to see those "social websites" icons {and load the data from those domains} get Fanboy’s Social Blocking List‎ for uBlock Origin or whatever ad blocker you are using.)

I agree NoScript is very important and have used it 'religiously' since it first came out in 2004, but within the last 7 or 8 years I have been using it "globally allowed". IOW, not blocking any domains; but all the other features of NoScript still work, like XSS (cross-site scripting), ABE (Application Boundaries Enforcement), ClearClick protection, along with the Trusted / Untrusted user-set options and META redirection's warnings enabled.

I did that with a PC that I built in 2008 (WinXP 2GB RAM) and a newer one that I built in 2016 (Win7 32-bit 4 GB RAM) - both low end hardware builds to keep the price down; both for general internet use, not for any type of gaming.

My advice it to try setting NoScript to "globally allow" all domains and see if that helps you.

In other words, you've decided there is no longer ANY malware being distributed via Javascript from untrustworthy domains?

Nice little imaginary universe you have there...

BillM said

In other words, you've decided there is no longer ANY malware being distributed via Javascript from untrustworthy domains?

I don't think that's what he is saying at all. There certainly can be a security/privacy risk to allowing scripts to be loaded from multiple domains. However, these risks are normally mitigated by security software, Firefox security features and safe browsing practices.

What I believe the-edmeister is trying to say is that it's normal for mutliple scripts to be loaded now. Back in the day, websites were pretty basic and didn't really require a lot of scripts. However, things have evolved a lot and there are often many scripts being loaded that aren't malicious. Consider this example:

You go to a news website. This website is tracking your visit for analytics purposes, so a script is being loaded from their tracking provider. The website is playing you an ad, so this loads a script from the ad provider. There is a Facebook share button, so there is another script. They also have share buttons for Twitter, Google Plus, LinkedIn and two other social media websites. That's another 5 scripts loaded from 5 different domains. Then, let's say that the website has a video player to clip a news clip. They could be using a library for that functionality instead of designing it on their own. That's another script. And look, they've embedded a Tweet as a source. There's another script. And finally, they are using Jquery instead of Javascript, adding another script to the grand total.

In this hypothetical example, that's a grand total of... 11 external scripts loaded, none of which are harmful.

That's not to say that a website can't exploit this to put malicious code on your computer, but most trustworthy websites don't.

The main point is, NoScript (although it's a great tool) can really slow your browser because it creates a lot of extra work. We are simply suggesting trying Firefox without that extension to see if it improves performance at all.

There is no PERFORMANCE problem; my laptops work as speedily as ever.

The yellow bar is an (apparently) MEANINGLESS warning. So far, no one at Mozilla has apparently *looked at the code* to see exactly what code conditions *trigger* the yellow bar. Is that too much to ask??

Please NOTE: There is NO public evidence to indicate that it's scripting-related AT ALL. I get it several times a week, whether I have enabled or blocked Javascript, and it's not correlated to any specific websites.

I'd look at the source code myself, but of course I don't have it.

The yellow bar's presence in released versions of Firefox is A BUG. I will escalate to bugzilla - but I don't have an easily-reproducible test case... it doesn't happen often enough... but it gives Firefox and Mozilla a black eye.

The bug's continued presence in the most-current Firefox release (64.0.2) indicates that Mozilla doesn't care much about their primary product. (Noted: statistics show Firefox is now a fairly-distant 3rd-place in market share.)

Tangentially, what is the Firefox Software Updater that was downloaded, this morning, to deliver 64.0.2, with no warning?

Overall, not very professional... long-term community members deserve better.

This is not the place to debate the success or future of Firefox. No one here is going to "look at the code" for you because that's simply not what this forum is for.

My recommendation is to run Firefox in Safe Mode to see if the issue is also present in there.

If your issue continues in Safe Mode, file a bug report and, if there is an actual issue that needs to be fixed in the code, it will be handled there. If the issue is gone in Safe Mode, you are welcome to file a bug report, but it likely won't result in anything since the developers will just tell you the same thing that everyone has told you here about browser addons and system performance.

The great thing about open source software is that you can look at the code yourself if you really want to. Read Viewing and searching Mozilla source code online for more information on that.

I'll look into that. (The good news is the yellow-bar only appears about 2x/month now... though it still represents a B U G.) Someone familiar with the code could undoubtedly fix it in minutes.

The (worst) current problem is memory: as noted earlier, Firefox takes twice as much (or more) memory as Chrome. 464MB to load and render "about:blank" is insane.

BillM said

The (worst) current problem is memory: as noted earlier, Firefox takes twice as much (or more) memory as Chrome. 464MB to load and render "about:blank" is insane.

If your only goal is to open and render the "about:blank" page, you should go to Options, scroll down to Performance, uncheck the Use recommended performance settings and lower the Content process limit to 1. It will make this task less memory consuming.