Hello guys.
I run into this problem for one year, see link text if you are interest into the old story. But it becomes serious after I upgrade to 1.7.4 in which the header was switched off by default.
Whenever I want to save my customized CSS or Header :
NodeBB encountered a problem saving changes
By the suggestion by @baris in this link , I modify it to message: err.message, then it becomes:
Changes Not Saved: unrecognized input
What am I supposed to do?
Thank you very much 
Below is my CSS:
body {
font-family:
"Times New Roman";
}
<script>
(function(){
var bp = document.createElement('script');
var curProtocol = window.location.protocol.split(':')[0];
if (curProtocol === 'https') {
bp.src = 'https://zz.bdstatic.com/linksubmit/push.js';
}
else {
bp.src = 'http://push.zhanzhang.baidu.com/push.js';
}
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(bp, s);
})();
</script>
Header:
<script type="text/x-mathjax-config">
MathJax.Hub.Config({
extensions: ["tex2jax.js"],
tex2jax: {
inlineMath: [['$','$'], ['\\(','\\)']]
},
TeX: {equationNumbers: { autoNumber: "AMS" } }
});
</script>
<script type="text/javascript"
src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
</script>
