there is a yellow line under the "debug" keyword(Undefined attribute name
"debug").
If i change the <s:head> to <sx:head> , then the yellow line will show under
'theme' keyword.
Any solution??
Perhaps checking the docs for the respective tags would help; I'm assuming you're using Struts 2.1, where the s:head and sx:head tags are different, and accept different attributes. The theme goes in s:head, the debug goes in sx:head.