4 types of borders

Dashed borders

You can specify dashed borders in the border property using the dashed parameter.

p {
    border-bottom: 1px dashed #000;
}

Example on JSFiddle

Dotted borders

You can specify dotted borders in the border property using the dotted parameter.

p {
    border-bottom: 1px dotted #000;
}

Example on JSFiddle

Double borders

You can specify double borders in the border property using the double parameter.

p {
    border-bottom: 3px double #000;
}

Example on JSFiddle

Gradient borders

You can specify the gradient boundaries through border-image property.

p {
    border-image: linear-gradient(to right, red, blue) 100% 1;
    border-width: 1px;
    border-style: solid;
    border-top: none;
}

Example on JSFiddle