Google AdSense

Do you regularly work with your webpages and AdSense implementation, tinkering with HTML or PHP and creating images and code on the fly? If you do, Firefox add-ons can help streamline the process of creating webpages. Here are some in particular that you may find useful:

ColorZilla
This extension tells you which RGB or hex color you're looking at, to help you make sure you created that logo for your business with just the right shade of blue, for instance. The tool also creates custom color palettes while you're browsing, so you can use them in your designs.

MeasureIt
Like the name says, use this add-on to measure the width and height in pixels of any element you see on a webpage. It's very simple to use, and you can define how much space you have left for that AdSense ad unit on the right-side. :)

IE View
Do you frequently use Internet Explorer to check how your website renders on that browser? This add-on allows you to view the way any page would look if it were opened in IE, without the hassle of opening another browser. You can also see pages that aren't Firefox-friendly much more easily.

WebDeveloper toolbar
This all-in-one toolbar gives you quick control over things like JavaScript display, form and CSS elements, screen resizing (so you know what your website looks like in smaller resolutions), HTML validation, and much more.