To add on to Petra's reply.
No it will not stop you from gaining in the skill.
I know squat about UOA.
If you are NOT at the Real SkillS cap, you will NOT be notified of the skill gain.
If you are at the real SkillS Cap and DO NOT have a skill turned down, then you will NOT gain in skills.
If you are at the Real SkillS cap and you have some skill turned down, then you will NOT be notified of the skill gain, but you will be notified of the skill loss, unless the down skill is also modified by an item, then you will not be notified of the loss (see below).
In the 2D client there are buttons at the bottom of the skill window for showing real / cap. You need to monitor where your Real Skills Total is in Relation to your Real Skill Total Cap. The Real Skil Total Cap can be found on the Characters Stat Gump. Your Health, Mana, Stamina Gump/Window, dbl click it and it gives you a more detailed Gump/Window. You can find your Real Skill Cap here. It will be a value from 700 to 720 in increments of 5.
In short, you only get a notification when there is an apparent skill level change.
Apparent being defined as Real Skill + SKill modifiers.