将之前做好的项目导入自己电脑的MyEclipse 出现如下错：The project cannot be build until build path

errors are resolved.
Unbound classpath variable: 'TOMCAT_HOME/common/lib/jasper-runtime.jar' in project 'dsrbSample'
Unbound classpath variable: 'TOMCAT_HOME/common/lib/jsp-api.jar' in project 'dsrbSample'
Unbound classpath variable: 'TOMCAT_HOME/common/lib/servlet-api.jar' in project 'dsrbSample'
我现在用的是tomcat6，之前的记不清楚了。当我在 右击→build path→configure build path→选择libraries选项卡→在下面选择TOMCAT_HOME/common/lib/jasper-runtime.jar后点击右边的edit，在弹出的对话框中将路径中的common去掉后，提示 Variable in the path does not exist.为什么呢？