If you are running a website, be it as a hobby, semi-professional or professional you need to know some tools of the trade. Webmaster tools can help the webmaster in many different areas like verifying that the website will display fine in all modern web browsers or ensuring that the search engines do not encounter problems crawling and indexing it.
The following list is a collection of webmaster tools that should help most webmasters. Many would consider them basic tools that every webmaster should know and use. Most of the tools are accessible from all operating systems and web browsers.
Google, Yahoo and Microsoft Webmaster Tools
Each of the three major search engines provides access to webmaster tools. These tools might require an account but will display all kind of information about the website that is related to the specific search engine. This includes crawling errors, statistics about indexed pages, sitemaps and troubleshooting help.
Google Webmaster Tools
Live
Yahoo Site Explorer

Markup Validation Service
The W3C Markup Validation services checks the syntax of webpages. It will report syntax errors which the webmaster should fix as soon as possible as invalid markup can lead to all sorts of problems including browser crashes, broken design or missing elements. It is a good idea to check the source check box on the page which will display the source code of the webpage which makes it way easier to locate the erroneous syntax.


Web Browsers
Testing websites in different web browsers is a must for every webmaster. What displays fine in Internet Explorer can throw up error messages in Opera or Firefox.
Firefox
Google Chrome
Internet Explorer
Opera
Safari
Web Statistics
Web Statistics are tools that record and analyze traffic that is arriving at a website. These tools provide extensive information about visitors (where do they come from, which pages did they access, how long did they stay), referring websites, errors and additional information. Webmasters have the choice to install a third party tracking code or run a web statistics script on their server directly. Running a third party tool will decrease the load on the server as no processing power is needed to crawl and analyze the access logs. Their disadvantage is that a piece of JavaScript has to be loaded on every user request which increases page loading times. It also means that data about the traffic is available at a third party site.
AWStats (Server)
Google Analytics (Third Party)
Sitemeter (Third Party)
Resources:
Robots.txt
Robots.txt files can be used to guide search engine bots on a website. They can allow or prevent access to certain files and directories.
Robots.txt
.htaccess
Htacess is a very powerful configuration option included in Apache web servers. It can be used to do various things like password protecting directories or redirecting 404 pages to another page.
Firebug
If there was one Firefox add-on that webmasters could use they would certainly pick Firebug. The add-on can be used to display realtime information about the active website in the web browser. Webmasters can select elements on the website to be taken directly to the code that is creating that element including its CSS properties. It can also be used to monitor network activity and to debug JavaScript. Several extensions are available for the add-on to increase the functionality further.
Firebug (requires Firefox)

Selenium
Selenium is a web application testing system for the Firefox web browser that can be configured to perform clicks, typing and other actions on the website which can be played back at a later time using variables like different web browsers or languages.
Selenium (requires Firefox)
If you can think of any other resources that are missing in this list let us know.
Related posts:
- Google Webmaster Tools Site Performance
- Mozilla Open Web Tools Directory
- Webmaster Contact Software
- Analyze Google Adsense statistics
- Verify Firefox Bookmarks With Check Places
- How To Handle Bulk Spam As A Webmaster
- Add Google Sandbox Search Engine To Web Browsers
- Firefox Spyware Add-On Adobe Flash Player 0.2

thans for telling me the firebug thingy.. I nvr knew tht one!! :)
Hmm, Thanks for the information.