Can you get a skill in RuneScape over 99?

Yes, if you drink a specific potion for that skill (Ex-Attack Potion will raise the skill level, I think, 5 points?) But there is a catch; you must have the skill cape equipped in order to have this effect. Otherwise, the potion will not do anything. Also Runescape is for 10 year old wannabe Warcraft nerds, and for ppl with absolutely no life

However, now you can have level 120 in dungeoneering to get the true skill master cape. So, Yes, you can have over 99 in a skill.