When writing your font stacks, be mindful that you probably don’t want Helvetica first in the stack. On Windows, at smaller sizes, Helvetica looks terrible. You want Windows to get Arial. Since you will want Macs to see Helvetica, you can put its digital brother Helvetica Neue first. This font is rarer on Windows and will often be skipped. It’s installed by default on Macs, so it will load. Don’t forget to include a Linux font, such as FreeSans or Nimbus Sans L. These can be listed first since Helvetica and Arial are less common on Linux.
font-family: "Nimbus Sans L", "helvetica neue", arial, helvetica, sans-serif;
(It could be argued that you don’t need Helvetica or Arial at all, only the Linux fonts given that they are defaults on Macs and Windows respectively. As long as you have the
sans-serif part at the end, you should be set.)