Definition of major, minor, and trace elements in analytical chemistry
There is no definite classification of what are the major, minor and trace elements are. While the numbers you mentioned are indeed the rule of thumb, they are rather loosely applied. It depends on field (geochemistry, solid state physics, analytical chemistry). There are however several guidelines.


Major elements are the elements that define the material in question. Some examples are: 


Gold and silver in electrum,
Yttrium, aluminum and oxygen in YAG,
Hydrogen and oxygen in the ocean.


If you change the major elements, you are essentially changing the material. If you replace the hydrogen with potassium then instead of water you will get potash, which is not the same material and has vastly different properties (although this example might be a bit extreme).
Major elements are usually measured in percentage (either mass or molar), and are commonly above 1% of the chemical composition of the material.
Trace elements are elements that occur in such small concentrations that they do not change the essence of what a material is. Some examples:


Copper and platinum in electrum. It's still a gold-silver alloy, just with some other metals. The properties (such as colour) may change slightly.
Neodymium, erbium, etc. in YAG. YAG is used to generate lasers, and doping it with trace amounts of other rare earth elements may change certain properties of the laser (wavelength). However, it's still a YAG.
Almost every other element other than H, C, Cl and Na in ocean water.


Trace elements usually have concentrations of below 0.1%. In this case it's easier to measure them in units of ppm (parts per million, this mostly refers to mass). Remember: 1% = 10000 ppm. In extreme cases ppb (parts per billion) may be the appropriate unit.
Minor elements are everything in between. Technically, this means things between 1% and 0.1%. You might think of sodium and chlorine in ocean water as an example of minor elements (even though they're both slightly above 1%). To be honest, other than a mention in introductory textbooks about analytical chemistry and geochemistry, I rare see this term used in the professional literature.