Pressing Ctrl while operating the mouse wheel is the standard operation for changing the page size, i.e. the size of all fonts and pictures on the current page and on any page subsequently opened.

Most browsers also have a setting (somewhere deep in the menu) to adjust the default font size, only effective for pages, such as normal Mudcat pages, that do not specify any font size themselves. Picture sizes will not be affected.

Both settings normally apply until changed once more.