What laptop? What are your laptop specs? What browser? What OS? What kind of websites, video, audio, plain text?
Depending on the laptop - opening 7 tabs with videos can be quite hard on the CPU and RAM which can cause your laptop to stop responding.
For example - with my system listed below - I can open about 4-5 tabs with videos, about 10 tabs with multiple pages of pictures and my system will start getting a little sluggish (only in the browser).