Sure, Firebug and Web Developer extensions for Firefox can do a lot of tricks. However, I have found that these web services are very useful in common web development tasks, and solve common tasks not accomplished by the extensions mentioned above.

Visual PageRank: PageRank is the measure of the popularity of a page used by Google – everybody wants high PageRank because it means that the page can generate lots of traffic from Google. You can view individual PageRanks with Google Toolbar, but it is daunting to check every pages in your website with the toolbar. Visual Pagerank provides an overlay on top of your website, showing the Pagerank of pages linked from a specified URL.

BrowserShots: There are hundreds of browsers in the world, how do you manage to view your site in all of them to ensure correctly displayed site design? Luckily, BrowserShots provides the answer by taking the screenshots for you in every browser you have heard of – there are even options for versions of Internet Explorer and Safari, so you can finally develop IE-aware (yuck) website in Linux. You must wait for a few minutes for the screenshot to appear, though.

Web Sniffer: Viewing HTTP headers is tricky because some of them redirect the browser to a new URL, so you cannot use the View Response Headers menu in Web Developer Toolbar. To remedy this problem, Web Sniffer features viewing all HTTP headers without redirection. It is a great tool to make sure that your redirections are correct, and a useful tool on its own in absence of Firefox.

popuri.us: PageRank is just one of the scores that is given to a page – Alexa have another ranking system, and the amount of links pointing to the page can be a great measure for popularity. With popuri.us, you can just provide the URL you want and popuri.us returns the PagRank, Alexa Rank, amount of backlinks, Technorati links, and many other measures used for ranking a page – all loaded with nice AJAX for speed.

IP2Location: Ok, this one got lucky because it is the first website I discovered – there are many websites providing the same service. Basically it shows the location of an IP address, down to the city level and the ISP. I thought this to be important because you need to know where your server resides – is it as advertised by the hosting company? It can also answer why a website loads so slowly, because the farther the server from you, the more hops that the data does before reaching you.

How about you? Do you have interesting web tools that aid you in web development?