in the same language editor mentioned above, instead of selecting from the "Choose Specific Language File:" drop-down list, type "All of the required fields are not filled in" in to the "Search String:" input box.
Click "Go"
Choose "Edit" from the left column of the one-item list.
At the beginning of bolded-red field, add a few line breaks.
UBBT7 DEFAULT:
All of the required fields are not filled in.
NEW:
<br /><br />All of the required fields are not filled in.
While you're on that same page, search for the "NO_PROCEED3" key ... towards the bottom 1/3rd of the list.
Do the same as we did above, but put the line breaks at the end of the string.
UBBT7 DEFAULT:
Please click <a href="javascript:history.go(-1)">[ Back ]</a> to return to the previous page.
NEW:
Please click <a href="javascript:history.go(-1)">[ Back ]</a> to return to the previous page.<br /><br />
Then click on either "Update Language File." button at the bottom.
Done.
NOTE: there are many different ways to make that message more visible (bolding, enlarging text, centering, different colors, using graphics, animated gifs, flashing text...etc), but spacing-it-out is the easiest and probably a more elegant solution.
EDIT FOR MINOR CORRECTION AND TO ADD: If desired, add a few line-breaks also ahead of the "Image Verification incorrect" string (NO_IMAGE_VERIFY key within that same generic.php language file)
