Highlighted letters in an email?

[Grandpappy]

I've re-installed Thunderbird and now if I click on any 'highlighted' letters or words,etc. nothing happens! Previously if I clicked on such a word or phrase I was sent to another connection or something. For example if I was looking at an article and it it said something like"to continue reading this article click on this link...." or suchlike (usually it was in blue lettering) I automatically transferred to another page or site;but nothing happens now,do I have to make some sort of adjustments? Any help please & keep it simple!!!
Cheers

[Grandpappy]

Use the "shift" key,dummy!