Here's the bottom line: If you use a font which isn't installed on the user's computer, the font won't display.

You can check out a thousand websites, and only find maybe a dozen fonts being used. Web designer's hard drive may contain scores of fonts (mine contains hundreds). But on the web, it does no good unless that font is on the user's hard drive, too. Otherwise, some generic font will be substituted.

Fortunately, there are a number of fonts which you'll find on most computers. There is nothing fancy about them--just ordinary text fonts, for the most part. But you need to use them when designing your site. The short list is: 

• Arial
• Comic Sans
• Courier
• Georgia
• Helvetica
• Impact
• Tahoma
  
• Times
• Trebuchet
• Verdana

The list is growing, and I could mention some others. But if you stick to the fonts listed above (as I do), you'll do fine.

At the most, use two fonts
Like the Healthy Ministry Resources website. Here, I use:

• Georgia (a serif font--serifs are those flags on the letters) for most body text (except on the blogs).
• Verdana (a sans serif font--no flags on the letters), for sidebars, captions, the blogs, and miscellaneous other text.

If you use just one font
Make it a sans serif font, like Verdana, Arial, or Helvetica. Those are the most readable on screen.

I like Verdana, because it was designed specifically for viewing on computer screens. Arial and Helvetica, on the other hand, started in the print world. I've designed several websites (like ub.org) using nothing but Verdana. For everything. I add variety by using bold and italics, and changing the type size and color, but it's still a single font.

In general:

• sans serif fonts are easier to read on a computer screen.
• serif fonts are easier to read in printed materials.