Hi Welcome to Sitepoint
It would help if you could post an example that illustrates the problem you are talking about more precisely as the issue mentioned could relate to many aspects. Have a look at the forum posting basics in order that we can help you better
It sounds as though you are confused about resolution and what happens on different monitors. You don't really need to know about any of that if you create a responsive site. What you should be concerned with is the width of your page and if you have defined that as a fixed width then it will not adapt to changes in viewport size or indeed resolution changes (at low resolutions you have less width to play with).
You need to create a page that has perhaps a max-width but is the fluid throughout any smaller widths. You can test this by simply making your browser wider or smaller (grab the edge) and open and close. Your layout should be created so that it adapts to the various widths throughout the whole range. There is no automatic way to do this; you have to make sure it happens by using media queries or a very fluid design.