This is a safe website. I suspect people who have rated it adversely are dog thieves who are trying to destroy the reputation of this charitable organisation. They have been interview on the BBC this morning, in connection with rising numbers of dog thefts, and the BBC do not broadcast interviews with disreputable organisations.
I'm the current (2010+) developer of doglost.co.uk - yes, older versions of the site (by other developers) were targeted by hackers. No site can be 100% secure, but the current site is far more secure than it was. If you see a problem with a website, don't just down-rate it - tell the webmaster.