Say I have the following code:
Hello world!
And the following CSS:
span{
color:red;
}
This is not possible, not even with CSS3. Here's an interesting article on text effects you can use with CSS3.
http://www.catswhocode.com/blog/8-examples-of-stunning-css3-text-effects
Another option is to use a custom font which suites your needs.
This site has an amazing amount of free open-source fonts in every format needed to support all browsers, it even gives you a nice demo file to demonstrate how to implement it in CSS. This is compatible with CSS2.1 as well, making it IE7+ compatible.
http://www.fontsquirrel.com/