Sometimes when you try to edit the source HTML of the page editor, you need to syles. The page accept your styles except one of them which is “background-image”. SharePoint consider this style as dangerous. Now when you write the follwoing in your HTML editor:
now save the page and try to edit it, you will notice that the background-image removed.
- Open SharePoint designer
- Create a new html page
- Write down you html with css
- Go back to you sharepoint page and edit it
- Add the web part “Content Editor”
- Edit the web part properties.
- In the Content Link, write the path to you HTML page