Most of the time, I am having problem with Internet Explorer 6, which most web designers tend to ignore nowadays. Sometimes, you find that the spacing is different. Sometimes, the alignment is different. These are minor problems that you can't really recall it very well, but it always happen.
You could be spending only few minutes to fix it, and that few minutes can turned up to be few hours of research.
If I can test my system on Firefox and Internet Explorer, can I actually test everything on Opera? Safari? (Yeah, I am the sole programmer and the tester of all my systems! My office is still on the way..)
To avoid spending unnecessary time to deal with the minor problems, I locked my systems to run on Mozilla Firefox only. I'm not sure whether it's a good move, but at least I have a small group of users which I can control and force them to install Firefox.
Finally, I found a website that has the ultimate answer: Do websites need to look exactly the same in every browser?
Anyhow, I would still spend time to make sure my system acts the same in every browser, if possible.. How about you?
If my article helped you solved your problem, consider buy me a beer!