In Firefox, the vertical scrollbar disappears when content fits inside the viewport. This makes several layout types shift position, typically by 10 to 20 pixels.
You can make the vertical scrollbar visible all the time. Read the instructions below:
Always Visible Scrollbar
like Internet Explorer.
1. Open the HTML Editor/ Text Editor or Notepad
2. Copy & Paste following code snippet
:root {
overflow-y: scroll !important;
}
3. Save this file with name userContent.css in following path
C:\Documents and Settings\[Windows Login Name]\Application Data\Mozilla\Firefox\Profiles\[profile name (random string of 8 letters, a dot (.) followed by some more letters)]\chrome\
4. Restart Firefox
