My apologies for not explaining the problem I have very well.
I have checked on my wifes computer and it does not show up the problem on the same internet sites, also sometimes the screen appears slow to react to the mouse. I feel it is something on my computer.Have checked for viruses and have Mcfee security if that is any help.
Have uninstalled yontoo 1.10.02 (which I don't know how it got there) and the problem of missing lines has disappeared and everything on the internet looks OK now which certainly suprised me , I'm not complaining anyway if it solves things Ok then.
Thank you for the replies