One of the most problematic for web designers are typography. It's related to fonts being used in a website. Different font results in different view and each browser (and also operating system) comes up with different font list, making it harder.
Good for all of us that there are several "safe" fonts. When you use an uncommon font and the client doesn't have that font, the browser will use the closest one available on their list.
To compare which fonts are good enough for your website, you can use Typetester, an online and live font comparator. Pick your font, size, and many other attributes and it will be displayed at your screen.