One of the things that people do with documents is to highlight passages of particular interest with a marker pen usually in fluorescent yellow or pink or orange. You can do the same thing with word processor documents in Microsoft Word which has a highlight facility to as the tool tip says “make text look like it has been marked with a highlighter pen”. This facility is also provided within Firefox through a number of add-ons which can be used to tailor your browsing experience. However, although there are a number of add-ons they work in slightly different ways.
The Highlighter add-on
This add-on works fairly straightforwardly. Once downloaded, if you select some text and right click on the text, you get a highlight option. The blurb states that if you use [Shift] and right-click you can choose your highlighting color, but I found that this did not always function reliably on my setup (Firefox 3 running under Vista). Worse, when I moved away from the page, the highlighting was lost, which seemed to undermine this add-on’s usefulness. A glance at the version date suggested that it had not been updated since 2006, so this may account for some of the limitations although it does validate as version 3 compatible.
The TextMarker add-on
This add-on is of similar vintage to Highlighter but is incompatible with version 3 of Firefox, so I was unable to test it.
The Diigo add-on
At the other end of the spectrum is Diigo. This offers a whole range of flexible functions including highlighting and Post-it notes that can be added to pages and will stay attached to your pages. It also allows you to take your bookmarks with you wherever you go (see https://www.brighthub.com/office/home/reviews/29332.aspx to compare this functionality with the Scrapbook add-on) and share them with colleagues and friends. However, in order to take advantage of this you need to join the Diigo social networking site. If you are a Facebook, Twittery kind of person, this may be just what you are looking for: if not, it may seem like a step to far just to highlight a phrase in a document!
The Wired Marker add-on
Wired Marker is commercial freeware rather than open-source. It offers a modern up-to-date solution with some useful options but without the complexity of joining a whole social networking site. To highlight, simply right-click and select the top option Highlight. A further sub-menu offers a choice of highlighter colors. A highlighted section can also be removed by right-clicking. The highlighting stays on the page until removed. It is the most popular of the highlighter add-ons in terms of downloads, and the online reviews are generally favorable with some users complaining of its complexity and others highlighting specific gripes with the latest (Feb 2009) version..
The facility to highlight text on a web page seems a good one. Of the add-ons available, Wired Marker seems the best option unless you want the social networking facilities of Diigo.