You can remove the shadow underneath the header or plugin slider for some theme that have it.
Step1: Open main_style.css
Click in to “design” and into “edit html/css”
Click open the main_style.css to access the css editing page
Step2: Locate code
Here look for this code:
Depending on your theme, you might have something slightly different. The important part here is to locate the shadow background code highlighted above.
Delete the code to remove the shadow. The final code will look something like this: