Are you using Live Search with a Stacks Framework like Foundation?
By default, Live Search will scan through the contents of the Stacks page "stacks_top" element. This element contains all the content added to the page through the Stacks editor. When using a theme none of the website components (like the navigation menu, footer menu, site title, etc) are found inside the "stacks_top" element, however this is different if you are using a framework like Foundation. This means that all elements on the entire page are now scanned because the entire structure of the website is inside the Stacks editor.
Specify a search container
To get around this, you can use the "Declare search container" to set your own element to scan. To do so, first locate a stack that contains the content you would like to limit the search to. If no single stack contains all of the content, you can add a single column stack to the editor and place it all inside of that stack. Select the stack and in the HTML > CSS classes field add a unique class name like "search-container".
Then in the Live Search settings enable Advanced Options > Declare search container and add the class name you created before, adding a period "." before the name
Now the search will only scan through the text found inside of this container.