In a perfect world, I don’t use CSS hacks, and certainly don’t recommend them. In the unpredictable, chaos of the real world, however, there are many situations where applying styles to particular browsers is indeed the optimal solution. Most of the time, I am targeting or filtering Internet Explorer (because it is so incredibly awesome), but occasionally I need to tweak something in a modern browser like Firefox, Safari, or Opera. In this article, we’ll look at CSS hacks targeting different versions of Firefox.

Some of these CSS hacks don’t validate, others are proprietary, and some are completely valid (depending on CSS specification). I have tested these hacks to the best of my ability, but don’t let that stop you from checking things out on your own (in fact, I absolutely recommend doing so). These Firefox hacks are organized according to version number and presented with ease of copying and pasting in mind. That said, here are some notes that apply to all of the hacks in this article:

• For each hack, change only #selector, .selector, and of course the declaration blocks.
• Hacks that do not validate as CSS are designated with [!] in the associated comment.
• If you discover any inconsistencies, incompatibilities, or inoperabilities, please leave a comment.
• This post is a work in progress. Please share any Firefox hacks that are not on the list.

Also keep in mind that, in general, there are two types of CSS hacks: those that target and those that filter. By targeting, we are referring to the application of CSS styles to a particular, targeted browser (or set of browsers) at the exclusion of all others. Conversely, by filtering, we are referring to the application of CSS styles to every browser except a particular browser (or set of browsers). In essence, this hack dichotomy represents two sides of the same coin. How you classify these various hacks all depends on perspective.

CSS Hacks targeting all Firefox

These hacks target all versions of Firefox:

/* Target all Firefox */
#selector[id=selector] { color: red; }

/* Target all Firefox */ 
@-moz-document url-prefix() { .selector { color: red; } } 

/* Target all Gecko (includes Firefox) */
*>.selector { color: red; }

CSS Hacks targeting Firefox 1.5 and newer

This hack targets Firefox versions 1.5 and newer:

/* Target Firefox 1.5 and newer [!] */
.selector, x:-moz-any-link, x:only-child { color: red; }

CSS Hacks targeting Firefox 2 and older

These hacks target Firefox 2 and older:

/* Target Firefox 2 and older [!] */
body:empty .selector { color: red; }

/* Target Firefox 2 and older */
#selector[id=SELECTOR] { color: red; }

/* Target FireFox 2 and older [!] */
html>/**/body .selector, x:-moz-any-link { color: red; }

CSS Hacks targeting Firefox 3

This hack targets Firefox 3 (and possibly newer):

/* Target FireFox 3 [!] */
html>/**/body .selector, x:-moz-any-link, x:default { color: red; }

Got more?

Please help by sharing any Firefox hacks that target or filter specific versions of Firefox. Bonus points for anyone with a hack for filtering all versions of Firefox (and only Firefox).

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