1. Firefox

I recommend Firefox as a primary browser for anyone, whether you are a Designer, Developer or Consultant. Not only does Firefox have fewer security vulnerabilities compared to Internet Explorer, it loads websites faster, and there are a lot of free Add-Ons that you can install to add extra functionalities to the browser.

2. Web Developer Toolbar (Firefox Add-On)

Web Developer Toolbar is one of the essential tools for Web Developers and it helps analyse a website easily and makes a developer's life easier. But it is also a handy tool for SEO consultants. If you haven't already got Web Developer Toolbar installed on your Firefox browser, you can download it from the Firefox Add-Ons site.

Here are a few useful tricks that a SEO consultant can make use of with the power of Web Developer Toolbar.

2.1. Disable Javascript

We know Search Engine Spiders are not able to execute javascripts. Therefore, 'Disable Javascript' option in Web Developer Toolbar helps you browse the website via a Search Engine Spider's view.

2.2. Disable Styles

To find out how a webpage is structured without any CSS styling which could be used to laid out the page differently to the order they appear in code, you can disable all styles on a page: CSS -> Disable Styles -> All Styles (Shortcut: Ctrl + Shift + S).

2.3. Alt attributes for Images

Search Engine spiders are not humans and hence, they are not able to view images on a website. You can disable images on a web page and replace them with alt attributes easily with Web Developer Toolbar: Images -> Replace Images with Alt Attributes.

But sometimes, you just want to check if images have appropriate Alt attributes, but not disable the images completely. In this case, you can do: Images -> Display Alt Attributes to have an Alt Attribute of an image appear on top of itself.

2.4. View Meta Tag Information

With Web Developer Toolbar, you can view Meta keywords and Meta descriptions in one click without having to view the source. Information -> View Meta Tag Information will display all meta tags on a page.

3. SEOpen (Firefox Add-On)

SEOpen provides basic tools which are used by SEO Consultants in optimising any website. Some of the useful things you can do with this toolbar:

3.1 View Backlinks in Google, Yahoo!, MSN, Alexa

3.2 View Pages Indexed in in Google, Yahoo!, MSN, Alexa

3.3 View Robots.txt

3.4 Check Keyword Density

4. Google Toolbar

Google is the mother of all search engines and Google Toolbar for Firefox adds many features that lets you obtain useful information from google via the toolbar.

4.1 View Page Rank
You can find out the Page Rank of the current web page you are viewing without using any other page rank checking tool. Make sure you have PageRank and Page Info checkbox ticked under More tabs in Google Toolbar Options in order to use this feature.

4.2 Find out Popular Searches
As you type in the search box from Google Toolbar, it will suggest popular searches which helps you identify what most people are searching for. To enable this option, go to Google Toolbar Options -> Features -> Search Box Settings, and tick Suggest popular searches. Here is a bonus link, someone did an experiement with Google Suggest to find out most popular questions being asked on Google.

5. SeoQuake SEO Extension (Firefox Add-On)

SeoQuake SEO Extension shows useful parameters both on web pages and search results pages, which means you can find out the PR of a page, Age of a domain, Total pages indexed, Alexa Page Rank etc without leaving the search results page.