Modify your style sheet and look for the paragraph below (usually at the beginning)
a {
color:#3399FF;
font-weight:Normal; /*The font effect can be changed to bold* /
text-decoration:none; /*Underline effect: no underline*/
}
a:hover {
color:#4499EE;
text-decoration:none; /*Underline effect: no underline*/
border-bottom: 1px #0099CC dotted /*Add a box with only the bottom border as dotted line*/
}
a{} controls the effect of the connection a:hover{} controls the effect of moving the mouse up.
Some CSS definition dotted line example code