Difference between "a" and "a:link"

Not quite sure what you mean with "covers both of them"... Look at the following example

a
{
  color: orange;
}

a:visited
{
  color: lightblue;
}

With this code everything works as intended. Unvisited links are orange, visited one light blue. It doesn't seem to make a difference if I add :link to the first rule or not.

With

a
{
  color: orange;
}

You say: Both visited and unvisited links should be colored orange. Since in CSS you can overwrite previous lines (the last written line of code for an element will be executed) you won't see the effect of this, because with

a:visited
{
  color: lightblue;
}

you say your visited links should be colored light blue.

If you use:

• a : Both visited and visited are selected

• a:link : Only unvisited links are selected

• a:visited : Only visited links are selected

This is strange...what you say makes perfectly sense, but to try it out I switched the above code sample and it still works. To be clear: now I have a:visited first (light blue) and a second (orange). Now the links should be orange, no matter what because a overwrites a:visited, right? But I still get the blue visited links.

Only if I add !important to the a-rule every link turns orange...

Is this maybe because a:visited is more specific?

Correct, the most specific will be used:

To make an example

• "*" (The selector which selects all elements) has a calculated specificity of 0,0,0,0

• a has a calculated specificity of 0,0,0,1

• a:link has a calculated specificity of 0,0,0,2

Higher number is higher specificity, higher specificity has higher priority.

If you want to learn more about specificity and importance: http://www.w3.org/TR/CSS2/cascade.html#specificity . It explains when something has priority over another.

Thank you very much for your help! :)

No problem, good luck with developping! :)