Are you testing against Chrome?

What are your browser-usage stats? You must start there. Every app's userbase is different. Rank the browsers based on those stats, and test/bug-fix in that order. That will, in most cases, give you the best bang for your time/money.

How can you track browser usage stats? Analyze your web server's logs or use Google Analytics.

For example, I know a B2B web app with 5000 users that have these ratios:

• 90% IE (6,7,or 8)
• 8% Firefox
• 2% Chrome
• Safari, etc are negligible

So they should:

• do complete full-featured tests with IE
• test only core features and general CSS compatibility with Firefox
• disregard other browsers

What if they have automated testing (i.e. Selenium)? Then testing all browsers is trivial. But you could still apply my logic to browser-specific bug-fixing. That cannot be automated. And the business will have to triage what bugs get fixed.

Certainly, this answer is subjective. Perhaps the 2%-chrome users are the highest paying users. I don't know. Consider your browser usage stats, your most important users, and the dev/QA resources available.

I test on chrome first, FF second and IE last...

When debugging JS I use Firefox Firebug...

Chrome is using the Webkit rendering engine similar to Safari. So, if your site looks bad on Chrome, it'll probably look bad on Safari...

I test on IE, FF, Chrome and Opera (and occasionally Safari). You really have to these days. For debugging Javascript I tend to use Chrome for its console, and sometimes Firebug in FF - they're both very helpful.