The Grid Guide provides a visual reference of the pixel positions of the various objects you have added to the page. (The Grid Guide looks like graph paper or a window screen in the background of the Work Window. It does not show up in the published page. For more information, see Grid Guide.) While the Grid Guide can help you align your screen elements, it does not prevent misalignment.
The Snap Grid takes some of the guesswork out of using the Grid Guide. With the Snap Grid enabled, when you move an object in the Work Window it jumps to the nearest grid border. It’s a timesaver – just click and drag objects to the same approximate location on the page that you want them, and – snap! – the Snap Grid finishes the job and aligns them precisely.
The pixel distance between snap grid borders is 10, by default. However, you can change the setting using the Snap Grid Resolution control on the Guide/Display Options dialog box (Options>Guide/Display Options) Lower resolutions offer finer control and less “snapping;” higher resolutions will more easily “snap” objects but may crowd objects unintentionally.
You can toggle the Snap Grid off or on by selecting ViewEnable Snap Grid, or by pressing the CTRL+M keyboard shortcut. Or, you can select/deselect the Enable Snap Grid option box on the Guide/Display Options dialog box. (For more information, see Guide/Display Options Dialog Box.)
The Snap Grid and Grid Guide are controlled separately. The Snap Grid will work even when the Grid Guide is turned off and not visible in the Work Window.
You can also transform or resize objects with the Snap Grid enabled in order to stretch or skew them in precise degrees or pixel increments. For more information, see Transform Object.