This question already has an answer here:
I see this character in Firebug 
.
I don't know why this is happening, there's no such character in my code. For Firefox it's OK, but in IE everything breaks. I can't even search for this character in Google.
I saved my file with utf-8 encoding without bom.
Before clear space (trim)
Then replace with RegEx
.replace("/\xEF\xBB\xBF/", "")
I'm working on Javascript, I did with JavaScript.
If you have a lot of files to review, you can use this tool: https://www.mannaz.at/codebase/utf-byte-order-mark-bom-remover/
Credits to Maurice
It help me to clean a system, with MVC in CakePhp, as i work in Linux, Windows, with different tools.. in some files my design was break.. so after checkin in Chrome with debug tool find the  error
Here's my 2 cents: I had the same problem and I tried using Notepad++ to convert to UTF-8 no BOM, and also the old "copy to MS notepad then back again" trick, all to no avail. My problem was solved by making sure all files (and 'included' files) were the same file system; I had some files that were Windows format and some that had been copied off a remote Linux server, so were in UNIX format.
Try:
copy this code to php file upload to root and run it.
for more about this: http://forum.virtuemart.net/index.php?topic=98700.0
yeah, its so simple to fix that, just open that file by notepad++ and step follow --> Encoding\ encoding UTF-8 without BOM. then save that. It work for me as well!
The character in question

is the Unicode Character 'ZERO WIDTH NO-BREAK SPACE' (U+FEFF). It may be that you copied it into your code via a copy/paste without realizing it. The fact that it's not visible makes it hard to tell if you're using an editor that displays actual unicode characters.One option is to open the file in a very basic text editor that doesn't understand unicode, or one that understands it but has the ability to display any non-ascii characters using their actual codes.
Once you locate it, you can delete the small block of text around it and retype that text manually.