NewInstance

With Firefox you can define your preferences on how Firefox should display the web sites you visit. To do that, there’s a file called userContent.css in user home directory (in windows it’s placed on “C:\Documents and Settings\[user]\Application Data\Mozilla\Firefox\Profiles\[8digits].default\chrome”); modifying this file you can, for example, modify default font style and size, to make website more readable.

With Firefox 1.5 there’s a new selector that makes it possible to define in userContent.css web site specific style. So you can add some style definition that will be applied for specific sites. The syntax is the following:

@-moz-document url-prefix(http://www.mysite.com/)
{
   /* define here specific css for http://www.mysite.com/ */

   /* example:
   div.rightbox {
      display: none !important;
   }
   */
}

I think that this is a cool feature. For example, I use Adblock plugin to remove ads from my favourite web sites. Combining new css feature in userContent.css with Adblock plugin, it’s possible to filter any ad from your favourite web sites, despite they use images, flash, javascripts or simple html:

Before and After the cure: at left, in internet explorer with all ads (in red circles); at right, the same site in Firefox using custom CSS and Adblock