System Tips: Learn more about vista protection mode

Don't know how many users are using vista?
vista protection mode
In recent days, IE has found a new development under the embrace of vista, with a protection mode. (internet option -> security -> enable protection mode)
This mode uses my understanding that IE forms with different "security levels" are not allowed in an IE process.
Here I first explain what is different "security level", maybe everyone's understanding is different —— for example, trust sites and ordinary sites are not a security level.
Raising the problem
Oh... what's the problem with that?
A domain that joins a trusted site, such as a.site.com. A normal site b.site.com.
When opening an IE process and opening b.site.com, this time you enter a.site.com in the URL (or have a link chain to a.site.com), you may not be able to open a.site properly. .com, or the prompt about:protectedmodeoff.
Solution?
When you encounter such a problem, the solution is to first add a.site.com and b.site.com to the same security level. However, the standard is not a standard, unless you are using the internal network, if it is used on the Internet, it is not feasible.
Server Transfer~
The example of the solution is not written much.