If you are like me, you spend a lot of time using firefox. Chances are that you don’t use it as effectively as I do. 
Let’s start with the look. First, use a minimalistic theme. I use full flat, but whiteheart is also kind of cool. Such themes simply don’t get in your way, which is exactly what you need.
You probably use several toolbars which take way too much of your screen space. Right-click on a toolbar and select “customize”. Then you can drag everything around and hide the unused toolbars. I currently have three rows of toolbars:
- First toolbar has File, Edit, View menu and others, back, forward, reload, cancel, home icons, location bar, and finally a search bar.
- Second toolbar contains quick bookmarks – just the pictures without any text, so that I can fit in as many as possible.
- Third toolbar is shared google toolbar (used mostly just for PageRank), webdeveloper toolbar, user agent switcher and adblock settings.
I often see people wasting their screen space by using the default configuration with menus in the first toolbar and action icons and location bar in the second one.
Speed up firefox by installing fasterfox or simply google around a bit to find out (enable pipelining, disable ipv6, etc.).
Learn to use keyboard shortcuts:
- ctrl+T — open new tab
- ctrl+L — go to location bar
- ctrl+K — go to search box
- ctrl+up/down — switch search engines when in search box (don’t forget to order them in a way that suits you)
- alt+enter — open the search from search box in a new tab
- ctrl+shift+T — open an accidentally closed tab (you can even repeat this shortcut — superb!)
- ctrl+b — bookmarks
- ctrl+h — history
If you use a mouse, install and learn to use mouse gestures. At least the few ones for back/forward and open/close tab. I personally prefer FireGestures, as that is the only gesture extension that actually knows what I mean when I perform the gestures. 
Out of the helpful extensions that I use, I must mention at least Download Statusbar, Customize Google and Adblock Plus.
And I almost thought I wouldn’t make another post in March. 
I was thoroughly bored with the previous theme, and although I tried to revive it with the new header image, it was still bugging me. So I created a new one.
I had a draft of a new theme lying around for quite a long time, so I made few adjustments to it: made the code much longer and much less clean. But it seems to work.
Features of the new design include, but are not limited to:
- big letters in headings (big letters rock)
- even less images (none, except the two links to flickriver, smilies and images in posts)
- half-fixed-width half-fluid design (the design is fixed width, but the sidebar is fluid — works well for many different widths of browser (800px — the sidebar isn’t displayed, it’s accessible through scrolling; 1024px — sidebar in one column, 1280px — two columns, more px — more columns (it is capped at three columns)))
- emphasis on typography (lists, blockquotes, etc. are styled properly)
- lines vertically in synch (left column, middle column and sidebar)
- the old color scheme, I mostly like it and more importantly — couldn’t find a better one at the moment
- justified text (I’m still very unsure here — justified looks way better, but left-aligned is more readable)
Bugs of the new design include, but are not limited to:
- IE6 sometimes messes up the sidebar, not quite sure why
- Opera doesn’t keep lines in synch when there are smileys (and I thought I had the solution, sigh…)
- IE doesn’t align the comment date in the comment list (will look into that later)
Also, I spent ages dealing with various bugs in IE that caused things to disappear.
One such bug caused the sidebar not to appear (it was an absolutely positioned element next to a floated element — don’t ever do that), another sometimes caused titles to disappear (they were relatively positioned, now that they are static it seems ok, but I have no idea why). When repairing the sidebar, I had to move it in front of the actual content in the markup, which is wrong and I know it. I am sorry to all lynx/links users out there.
Bug reports, remarks and suggestions are welcome! 
Almost everyone, myself included, underestimates the basics.
If you want to be an expert in any field, you need very strong basics. When you don’t know the basics, you tend to make many mistakes which are hard to get rid of. We are ambitious so we dive deep into all sorts of advanced stuff, leaving the basics for later, perhaps thinking we will somehow figure the basics out along the way. This sometimes works, but more often it doesn’t.
So, back to the basics for me! (in what, you ask? — in everything!)