The LCase function converts a string to all lower case letters.

There is also a companion function UCase to convert to upper case letters.

Code:
<% =LCase("Aardvarks do not make good pets!") %>

Output:
aardvarks do not make good pets!

You can also use the name of the string.

Code:
<% astring="Leopards also make bad pets!" %>
<% =LCase(astring) %>

Output:
leopards also make bad pets!