<p>A block's visibility depends on:</p>
<ul>
<li>Its region placement. Blocks with no region assigned to them are never shown.</li>
<li>Its throttle checkbox when throttle module is enabled. Throttled blocks are hidden during high server loads.</li>
<li>Its page visibility settings. Blocks can be configured to be visible/hidden on certain pages.</li>
<li>Its custom visibility settings. Blocks can be configured to be visible only when specific conditions are true.</li>
<li>Its user visibility settings. Administrators can choose to let users decide whether to show/hide certain blocks.</li>
<li>Its user-role visibility settings. Administrators can choose to let blocks be visible only for certain user roles.</li>
<li>Its function. Some dynamic blocks, such as those generated by modules, will be displayed only on certain pages.</li>
</ul>
