correct tags for validating input types

There’s much more than just those three functions. As it would be too much to write 5 blog posts (or even a whole book) about it, I’m just going to give you some reads as starting points:

• One of the rare good articles on WP Tuts+ ¹⁾
• QueryPosts.com is the way to read source code, if you want to avoid digging into core with your IDE. ²⁾

^{1) If you wonder, why it rocks: It’s written by our own @StephenHarris 😉}

^{2) If you (are again) wonder(ing), why it rocks: It’s developed by our own @Rarst 😉}