For a juvie 100-110. Most like it more so in the 105-110 range though.
Adults (fully grown) typically like it a little cooler. 95-100 maybe 105. I wouldn't ever go under 95 for a basking surface though. There are minimum temp requirements the body needs for basic metabolic function and even 95 is cutting it a little low.
And remember the point is to at least have the temp there for them if they want it. If one spot on the basking surface is hotter than they want, at least they have the freedom to move a couple inches over to where it might be a couple degrees cooler. They don't have this option if your basking surface doesn't even get hot enough to give them the choice.
-Brandon