If you’ve been using Opera for a while there are a few things that you’ve probably are used to. I’ve been using Opera for so many years now and I’ve finally made my mind switching to Firefox 2. Here is how i configured my Firefox to offer me more or less the same functionality as Opera

Session Saving

It’s now a built-in feature in Firefox. Open the Preferences (“Main”) and set in “Startup” the “When Firefox starts:” to be “Show my windows and tabs from last time”.

Tabs – ONLY!

If you want to restrict no new windows to be opened, but tabs only you can set that in the Preferences “Tabs” – “New pages should be opened in:” … “new tab”.

Pop-ups Blocking

This is a built-in feature that is enabled by default. Can be disabled in the Preferences “Content” by unticking the “Block pop-up windows”.

Spell Checking

This is a built-in feature that is enabled by default.

Mouse Gestures

Firefox doesn’t have built-in mouse gestures support but there is an extension called All-in-One Gestures. By default it leaves a red trail when making a gesture and the click -> move down will not open a new tab. To fix those two.
Go in “Tools” -> “Add-ons” -> Click on “All-in-One Gestures” -> “Preferences”
-> “General Preferences” -> Untick the “Enable Gestures Trails” – for no trail
-> “Gestures Customization” -> “Open new Tab in Foreground” -> “Edit Gesture” -> Repalce “U” with “D” (for down) -> “Ok” and if it asks to swap gestures just say yes. – for new tab opening on click -> down gesture.

Closed tabs history

There is an extension available for that called Undo Closed Tabs Button. After installing it you will have to right click on Firefox’s Toolbar select “Customize” and then drag and drop the button to very right (where it is in Opera). By default it will save up to 5 closed tabs and will add a “undo closed tab” right click menu entries. To fix that:
“Tools” -> “Add-ons” -> Click on “Undo Closed Tabs Button” -> “Preferences”
-> Tick “Remove “Undo Last Closed Tab” from the right-click context menu”
-> Set the number of closed tabs to remember to the desired one.

Tab Preview

Firefox doesn’t provide a preview of the page when a tab is hovered, but there is a very nice extension called Tab Catalog. You can add it as a button to the toolbar or just hit F8 and it will show you a screen with large thumbnails of all opened tabs so you can just select the one you want.

Content Blocking

Install Adblock Plus and just forget about ads.

Image Filtering (Cached/All/None)

There is an extension available for that called ImgLikeOpera. After installing it you will have to right click on Firefox’s Toolbar select “Customize” and then drag and drop the button to the toolbar. By default it will make pages show only cached images that can be changed in “Tools” -> “Add-ons” -> Click on “ImgLikeOpera” -> “Preferences” -> Set the “Default policy for new window/tab” to “Load all images”

Side Bar

There is an extension available for that called All-in-One Sidebar.