When you check your created page on Preview or Live page, you may notice that there is a white space between the header and the main body of your page. 

This problem happens on specific themes only since this is a default padding-top of the themes’ layout. 

Option 1: Overlap the white space by using negative margin-top

From the editor, you click on the first element of the main content >> navigate to tab Design >> section Spacing >> then add a negative margin-top for that element. 

In this way, the first module will be pulled-up and overlap the white space.

Eg: I set margin-top: -55px for the first section of my page: 

Option 2: Adding custom codes to remove the padding-top globally

Besides the first way above, the white space also can be removed by adding the following CSS to the bottom of theme.scss.liquid file:

html.gemapp .main-content {
   padding-top: 0 !important;
   padding-bottom: 0 !important;
   margin-top: 0 !important;
}

Hope this helps. In case you need further assistance with this matter, please do not hesitate to contact us. We will be happy to help you.