it is extremely important that the adding of !important should not
be used in the off hand manner that you employ in your coding.
It can create more problems than it can solve.
Instead, improve your coding skills to make it’s use unnecessary.
This snippet…
.ad p {
font-size: 21px !important;
text-align:center !important;
color:blue;
font-family:"Segoe UI",Tahoma,Helvetica,Sans-Serif!important;
margin-right:10px;
}
…is rigidly setting the font-size that you are attempting to alter.
If the above answer is not to your liking then just use this mess…