Q:

CSS automatically disappearing from Content Editor web part

I'm adding some css in content editor web part on my aspx page and css applies well but as soon as I stop editing page css disappears. When I open the web part again I can see empty 
<style> </style>

tag. Any idea ? 
This page has custom web part and even if I add some inline css to the web part it applies when page loads but disappear when page finish loading..
I'm trying this on Firefox.

A:

Content editor web part does not let you embed style and script elements directly in the page. 
Instead, content editor web part lets you link to a css or js source stored in a sharepoint library.
Alternatively, use SharePoint Designer (if installed in your company) to inline style and script.

