I’ve been using the Internet Explorer Developer Toolbar for years with Internet Explorer 7 and below. When Internet Explorer 8 came out, it had these tools baked right in and called the Developer Tools. (You can activate the Developer tools by hitting F12 in IE8.)
But what if you need to peek into the DOM with Safari or Firefox? Here are the tools for the Windows platform:
From Safari help:
To examine the resources of a webpage:
Open the website, and then choose Develop > Show Web Inspector. The Web Inspector’s sidebar lists the categories of resources found on the page, such as documents, style sheets, and scripts.
Note:If the Develop menu does not appear in the menu bar, open Safari preferences, click Advanced, and select “Show Develop menu in menu bar.”
From the Firebug Web Site:
Visit the Firebug website for documentation, screen shots, and discussion forums: http://getfirebug.com