Helping people with computers... one answer at a time.

Javascript syntax errors on web pages could come from a number of sources. We'll start with a thorough malware scan.

I use Windows 7 and Firefox 17.0.1. For the past week or so, on most web pages I visit, I get a pop-up box that says "JavaScript application" in the top left and then error "syntax error" in the middle of the box. I've searched for answers but have found none that have helped. Can you tell me how I can stop this annoying error message?

In this excerpt from Answercast #95 I look at some odd javascript errors, possible causes and solutions.

Javascript syntax errors

Well, yes and no. I can only guess where that is coming from because it's unlikely that all of these different sites are actually using JavaScript - and all have a JavaScript error, an actual error, in what they've encoded on their web pages.

What's more likely is that there's something on your machine that is causing that.

Possible virus

Now there are two scenarios that come to mind. One is you have malware on your machine - or perhaps more correctly, you have an attempt at malware on your machine - that has left some kind of trace of malware in a way that is impacting your browser.

Maybe it's trying to hijack your browser, and is failing, or doing something else that has somehow caused a problem with your browser.

Browser add-on failure

Now, it could be an add-on. I would certainly start by disabling all of the add-ons.

More likely, though, is that this is malware. It's a bad install of that malware. Yes, malware is not perfect. It can in fact fail and fail in some very interesting and confusing ways.

Anti-virus scans

The very first thing I would do is to run a complete and fully up to date anti-malware scan - both anti-virus and anti-spyware if you have two separate tools

I would probably also grab a copy of the free tool from and run a complete scan with that as well.

Corrupt browser

The other thing that comes to mind is that something in the browser itself is corrupt. It broke for reasons unknown.

What I would do in that case (if the malware scan doesn't resolve the issue for you) is I would reinstall the browser. I would uninstall the browser completely first and then reinstall that browser.

Alternately you could switch to a different browser.

Software conflicts

While I was thinking this through a third option came to mind. That is that the anti-malware tools themselves could be impacting the browser.

Many anti-malware tools will attempt to scan any pages you're viewing as you're viewing them; as they get downloaded. That can interfere, at times, with the browser's access of those files; access of what's in those pages.

It's a complex timing interaction. It doesn't happen for everyone and it doesn't happen all the time.

The thing to look for there is to go to your anti-malware tools and make sure that anything that might be considered "real time scanning" of browser pages, of your internet browsing, is actually turned off.

You can temporarily turn off your anti-malware tools completely - but only do that temporarily just to see if the problem goes away. Turn them back when you're done.

What you're really looking for is an option that controls whether or not your anti-malware tools are looking at your web browser's pages as they are being downloaded. That can sometimes interfere with the browser in such a way that weird things like this can happen.

(Transcript lightly edited for readability.)

Next from Answercast 95- Why don't my speakers work?

Article C6321 - February 22, 2013 « »

Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

February 26, 2013 9:39 AM

If Oracle can't repair Java language with updates
why isnt Java banned ?

Mike Rosenthal
February 26, 2013 10:12 AM

I use Apache Open Office and often receive an ASCII error message when I try to open a file. If I click to open the file, all I get is gibberish. What's going on? And how can I prevent it? Should I be saving these files in a different way? Thanks for your response.

February 26, 2013 12:36 PM

I've had this happen. What I did was uninstall and reinstall whatever I thought was causing the problem. Browsers, anti-malware, and anything else that I thought might be involved. The un-re-install worked for me but 'your milage may vary'.

Comments on this entry are closed.

If you have a question, start by using the search box up at the top of the page - there's a very good chance that your question has already been answered on Ask Leo!.

If you don't find your answer, head out to to ask your question.