You can use the buttons on the links toolbar to manage the page the way you want it to display.
But if you want the settings to take the permanent effect, you have to change your default style sheet.
From Tools choose Options and on General Tab choose Accessibility.
1. Ignore colors specified on Web pages
2. Ignore font styles specified on Web pages
3. Ignore font sizes specified on Web pages

Or you can create your own style sheet.
Save the following style rules after making the necessary changes to your hard drive.

Always underline text links (IE, Mozilla)
:link, :visited { text-decoration: underline ! important }

Always show a border around image links (IE version)
/* This version breaks many site layouts! Use the Mozilla version if you can. */
:link img { border: 1px solid blue }
:visited img { border: 1px dashed purple }
:active img { border: 1px solid red }

Always use my chosen font type (e.g., Times New Roman)
* { font-family: serif ! important; }

From Tools choose Options and on General Tab choose Accessibility. Browse to the path of the recently saved .css file.