secure internet site restriction

[eboni]

I am trying to acces certain websites that are secured. i am a student and also a govt employee and can never access the needed pages at home. I am able to pull up all the sites intially, however when a certain page is neeeded i can not go any further, a yellow exclamation point appears in the lower left had corner of the screen. I assumed it was my internet provider but after a long month of back and fourth with them i discovered it is something blocking these sites in my computer. I have disabled all firewalls and deleted old internet files I do not know what else to do please someone help asap