Why is the em font displayed incorrectly on safari mobile (iPhone)?

Question

css

Good afternoon. There are three blocks .footer1, .footer2 and .footer3. In the .footer1 p style, the font is set to font-size:0.9em, and so are the links in the .footer3 style. The font of these elements must be the same size, as it is in all browsers on the PC, including on android. However, on the iPhone in Safari, the font of the links is larger than in the paragraph, what could be the problem?

#footer {
  width:90%;
  display: flex;
  align-items:center;
        flex-direction: column;
}
.footer1 {
  margin-top:30px;
  margin-bottom:12px;
  width:100%;
  float:left;
  position:relative;
  z-index:1;
  overflow:hidden;
  text-align:center;
  padding-top:2vh;
}

.form {
  display: flex;
  justify-content:center;
}

.mail {
  width:85%;
  max-width:470px;
  height:42px;
  background-color:transparent;
  border:1px solid #ccc;
  text-align:center;
  outline: none;
  position:relative;
  color:#f5f5f5;
  -webkit-border-radius: 0;
  border-radius: 0;
  box-sizing: border-box;
}

.button{
  background-image: url(../images/b.png);
  background-size: cover;
  background-position:center;
  width:42px;
  height:42px;
  border:1px solid #E73280;
  border-left:none;
  cursor:pointer;
  background-color:#E73280;
  border-radius: 0;
  box-sizing: border-box;
}

.footer1 p{
  clear:both;
  text-align:left;
  color:#f5f5f5;
  font-family: 'Ubuntu', sans-serif;
  font-weight:100;
  font-size:0.9em;
  text-align:center;
  margin-top:10px;
}

.footer2 {
  margin:0 auto;
  width:100%;
  margin-bottom:20px;
  float:left;
  position:relative;
  z-index:1;
  overflow:hidden;
  text-align:center;
}

.footer2 h5{
  font-family: 'play', sans-serif;
  font-weight:100;
  font-size:1.9em;
  color:#fff;
  font-weight:bold;
  margin:0;
  padding-bottom:1vh;
  color:f5f5f5;
}	

.footer3 {
  width:100%;
  margin-bottom:20px;
  float:left;
  position:relative;
  z-index:1;
  overflow:hidden;
  text-align:center;
}

.footer3 a{
  text-align:left;
  float:none;
  padding-left:2%;
  padding-right:2%;
  line-height:1.5em;
  color:#f5f5f5;
  font-family: 'Ubuntu', sans-serif;
  font-weight:100;
  font-size:0.9em;
  text-decoration:none;
}

.footer3 a:hover{
  color:#ccc;
}

Answer 1

http://ru.stackoverflow.com/questions/382661/How much...