「」
Google Toolbar — blocks pop-up ads
Literal
Popup-ad [obj-を] block 'Google Toolbar'
A headline-style noun phrase: the entire verb phrase ポップアップ広告をブロックする functions as a relative clause modifying 「Ｇｏｏｇｌｅ ツールバー」, with no finite verb or copula. The whole utterance is a caption/label, not a sentence. Note the full-width Latin letters (Ｇｏｏｇｌｅ) and full-width space, a Japanese typographic convention used so that embedded English reads at Japanese character width.