What should I do about the white border on the company's website (the code says#XFEFF;)

I believe many development partners have encountered this, and there is an inexplicable white border on the head of the website.

Looking at the source code, no exceptions were found, but through the F12 review element, we found that there was an extra line of code #XFEFF under the Body;

So how should we solve this problem? It is very likely that the code was not saved correctly during development. Let's just convert the code at the header back to the code and save it. Let's go and see if it has been solved.