Personal space. Web Designer Knowledge Base
The problem in question arises if there are such sensations from the layout: too much information, too crowded, too tight.
This means that for some key objects you have allocated too little free space spaces around. Each element of the site, as a person, needs its own space.
It is inconvenient to sit at the table when you are propped up with elbows on the left and right. It's inconvenient to drive in traffic when there are a lot of cars on the left and right. It's inconvenient to push in the subway when 10 flows of people converge on the escalator. It's unpleasant to talk with a person who crawls close to you.
If for a person, say, it is 1 meter in front / 2 meters in back / half a meter in side, then for each of the elements of the site this is its own space. P>
The rule is this: the more important the element, the more it should have personal space. The larger the object itself, the (proportionally) more it needs personal space.
If website design is done on a grid, often inside the column indent extra for some elements. This grid does not violate (in extreme cases, add more guides, and that's it).