Uzun kelimelerin otomatik olarak kesilip bir alt satıra inmesini HTML & CSS ile sağlayamazsınız.
Ya bir PHP fonksiyonu ile belirli bir karakter sayısına kadar uzun olmasına izin verecek, fazlasını kesmesini isteyeceksiniz ya da genişlik - yükseklik değerleri atayıp overflow: hidden ile genişliğe veya yüksekliğe sığmayan, taşan kısımların gizlenmesini ağlayacaksınız.

Örnek:

<div style="width: 500px; height: 200px; overflow: hidden; border: 1px solid #000;">
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 1<br />
    LoremIpsumissimplydummytextoftheprintingandtypesettingindustry.LoremIpsumissimplydummytextoftheprintingandtypesettingindustry.<br />
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 3 <br />
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 4<br />
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 5<br />
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 6<br />
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 7<br />
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 8<br />
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 9<br />
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 10<br />
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 11<br />
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 12<br />
</div>