Mouse-Keyboard Combo Tips
From MozillaZine Knowledge Base
Hold down the Shift or CTRL key when left-clicking on a menu item which represents a web page (such as an item from the Back, Forward, Bookmarks and Go menus) to open it in a new window or a new tab. This principle will work in many situations, such as on bookmarks, bookmark folders, history items, toolbar buttons, links and images. (Using Shift to open new windows is currently less well supported than using CTRL to open new tabs.)
To select text, left-click on part of a web page and then hold down Shift and use the arrow keys to make the selection.
Alternatively, left-click once in the window where you want the selection to start and then shift+click in the spot where you want the selection to end. This is a lot easier than click-selection-dragging.
Hold down Ctrl and scroll up down with the mouse to change font size. (Internet Explorer has five font sizes; Firefox has dozens.)
If you hold down the Ctrl key and left-click on part of a web page, that section of the page will be highlighted. If you right click on the selection and choose 'View selection source', the source code for that part of the page will be displayed.