Safari doesn´t keep the highlighted Text when I switch between Tabs

Hi everybody!

Here my trouble with safari:

1. I highlight a text in one particular tab (tab 1).

2. I switch the tab and go to another tab (tab 2).

3. I come back to the tab 1.

4. Trouble: the highlighted Text is not highlighted anymore!!!

I spend a lot of time googling for a solution but nobody seems to have this problem, quite strange.

Have somebody one Idea? It can´t be that difficult.