Q: Can anybody help me, My Safari wont open at all now, Im not sure if ive downloaded something corrupt to cause it to do this now, I changed over to yosimite few months ago

This can happen if adware  is installed without your knowledge. Removing it will help,

1. Download and use free AdwareMedic to remove the adware

    http://www.adwaremedic.com/index.php

    Install , open,  and run it by clicking “Scan for Adware” button   to remove adware.

    Once done, quit AdwareMedic.

               or

    Remove the adware  manually  by following the “HowTo” from Apple.

    http://support.apple.com/en-us/HT203987

2. Safari > Preferences > Extensions

     Turn those off and relaunch Safari to test .

     Turn those on one by one and test.

3. Safari > Preferences >  Search > Search Engine :

    Select your preferred   search engine.

4. Safari > Preferences > General > Homepage:

     Set your Homepage.

HI, I am having the same problem today.

I downloaded a program called Disk Drill but since then my Safari is crashing. I have uninstalled Disk Drill and any add ons but it is still crashing. I cannot download any programs as Safari won't open at all. Any help would be much appreciated.

The second post in this thread cured it Safari quit unexpectedly / Yosemite

I went to the app store and downloaded 'Sleipnir Browser' for free. That allowed me to download 'Adware Medic'. Which sorted it out thankfully.