Whenever you try to The character “&” is an ISO HTML reserved character used to denote the start of a parameter. The Blogger editor translate the “&” you enter to the HTML entity, “& amp ;” (without spaces between characters), that will display “&” when the page or URL is rendered in a browser.
However, in the html code editor in Blogger, the editor does not convert to “& amp ;” … and when the HTML editor detects “&” the code is not accepted. There for when a code snippet that you are using includes “&” … you must enter “& amp ;” (without spaces between characters) manually (instead of merely “&”).
Simply state: Replace “&” with “& amp ;”
See also …
support.google.com/blogger/thread/27902475/why-does-this-keep-changing-my-ampersand-to-amp?