Responding to repeating questions from clients and colleagues about recommended Firefox plugins for Web Development and basic SEO/SEM, following are the Firefox Addons I can’t do without :
ColorZilla web developer addon
It assists web developers and graphic designers with color related tasks.
With ColorZilla you can get a color reading from any point in your browser, quickly adjust this color and paste it into another program. You can Zoom the page you are viewing and measure distances between any two points on the page. The built-in palette browser allows choosing colors from pre-defined color sets and saving the most used colors in custom palettes. DOM spying features allow getting various information about DOM elements quickly and easily.
FireBug web developer addon
Webdeveloper web developer addon
The Web Developer extension adds a menu and a toolbar to the browser with various web developer tools.
MeasureIt web developer addon
Draw a ruler across any webpage to check the width, height, or alignment of page elements in pixels.
ScreenGrab web developer addon
An extension for Firefox that makes it easy to save a web-page as an image. With it, you can save anything that you can see in a browser window - from a small selection, to a complete page.
Live HTTP Headers web developer addon
View HTTP headers of a page and while browsing.
ShowIP browsing addon
A Mozilla Firefox extension which shows the IP Address of the current page in the browser's status bar and allows queries to different databases about it when you right click on it. The IP is colored red for an IPv4 address and green for an IPv6 address (hence the name). Since v0.7.8 these colors can be changed in the preferences menu. With a left click one can get information about the hostname of the current page.
IETab browsing addon
Embeds Internet Explorer in a Mozilla/Firefox tab.
YSlow web developer addon
YSlow analyzes web pages and tells you why they're slow based on Yahoo's rules for high performance web sites.
SearchStatus SEO addon
A toolbar extension for Firefox and Mozilla that allows you to see how any and every website in the world is performing. Designed for the highly specialised needs of search engine marketers, this toolbar provides extensive search-related information about a site, all conveniently displayed in one discreet and compact toolbar.
SeoQuake SEO/SEM addon
A Mozilla Firefox extension aimed primarily at helping web masters who deal with search engine optimization and internet promotion of web sites. Seoquake allows to obtain and investigate many important SEO parameters of the internet project under study on the fly, save them for future work, compare them with the results, obtained for other, competitive, projects.
Google Global SEO/SEM addon
Google Global allows users to see organic and paid Google search results as they appear in different countries, cities, regions, ZIP codes and IP addresses.
Some of those are quite basic and popular, yet some I’ve rarely seen others use. If you’ve got any other web developing or SEO/SEM Firefox Addon favorites, I’m interested.