This is what i was trying to do. make Startpage the default search .
"Q: Can I also use Startpage through the Firefox or SeaMonkey or Flock Internet Keywords search?
Using the Firefox or SeaMonkey or Flock browser it is possible to perform a web search just by entering your search term into the Location Bar and hitting "enter".
By default these browsers use Google, but you can easily change it to Startpage. Here's how:
*NOTE: Please make sure to follow the below directions exactly, as changing the "about:config" preferences can influence the behavior of your browser negatively.
Type 'about:config' in the browser location bar and hit 'enter'.
Accept the warning message to be careful.
Enter 'keyword.URL' in the filter on top of the page.
Double-click on the 'keyword.URL'- line that shows up.
In the pop-up window replace the Google string with: https://startpage.com/do/search?language=english&cat=web&query=
Click on 'OK'.
Close the window or tab.
Now, you are ready to search. If you type your search term into the Location bar, Firefox or SeaMonkey or Flock will submit a search query to Startpage since your search term is not a valid URL.
Every entry without a clear match to a URL will display the Startpage search results page for the entry and any settings you had saved before will be respected.
If you rather use the settings you generated in a URL you will need to amend https://startpage.com/do/search?language=english&cat=web&query=
Replace 'language=english' with 'prf=[complete prf-value]' or with 'prfh=[complete prfh-value]' from the generated url, and make sure there is no space before continuing with &cat=web&query= .
Found here. https://www.startpage.com/eng/company-faq.html#q13