Yea, online character sheets are notoriously bad with skills and multiclassing. Best way is to just figure it out, level by level.

There are 2 things to remember. Max ranks, and cost per rank.

Max ranks are determined by whether or not a skill has EVER been a class skill. Even if it was just for 1 level, and you didn't put any ranks in it then, the max ranks are ALWAYS LVL+3. If you've never taken a class with a skill as a class skill, its crossclass and max ranks are (LVL+3)/2 until the point where you take a level in a class that has a skill as a class skill.

Cost per rank is determined by what class you are taking at each level. If its a class skill for that class, you buy ranks 1 per point. If its not, you buy ranks 1 per 2 points.

Note that some things affect this. Human Paragon and Loremaster both make certain skills class skills for all of your classes. When this happens, pencil that skill in as a class skill for all classes and PrCs you take and buy ranks accordingly.

Make sense?